When I used to shoot Vallejo paints, I kept a shot glass half full of Vallejo thinner with a Q-Tip in it next to my spray booth. Every 3 minutes or so, when I would get tip dry, I would grab the Q-Tip, swirl it in the needle cup of my airbrush, and it would spray again. Repeat this drudgery every 3 minutes until you are done spraying. It’s a pain but it works. This was after adding flow aid and retarder.
Some guys have found the magic formula for Vallejo paints but I never did. They just clogged my airbrushes every 3 minutes. I tried everything and with 45 years of airbrushing experience and a drawer full of Iwatas, I couldn’t make them work for me. I had about 300 bottles of Model Air and Model Color and I sold most of them and gave the rest away to my club mates.
I switched to AK Real Colors thinned 50\50 with Mr. Color Leveling Thinner and never looked back. I get perfect airbrushing every time and I’m back to being happy with my airbrushes.
It’s not you, dude. It’s not your airbrush. It’s the paint. Vallejo Model Air and Model Color are Latex Acrylics and they aren’t designed for airbrushes.
But you’ll probably get a reply saying it’s not the paint.
Oh and yeah, you do have a bent needle, because you mentioned that the spray pattern had shifted - #1 sign of a bent needle tip.
I’ve noticed the Vallejo primer doesn’t sand well. For most small figures it’s fine, but for ships I use AMMO or Tamiya primers. I do use Vallejo paints, but they make up only 1/4 of my “stock”. I’ve been expanding into Tamiya and will probably check out AK as well. I’m far from an expert - but I am brand agnostic - so take all my opinions with a grain of salt 
I will say this; 80% of my paint stock is Vallejo; when I started this hobby (jeez, what, five years ago?) that was the only paint I bought. It suited my needs and I learned to work with it. I would just work around it not spraying correctly or not spraying at all. However, recently, I decided to pick up some Tamiya acrylics and see how those went. Safe to say, as much as I like Vallejo (and how much of it I have), I prefer Tamiya. I’ve had less issues and more durability with it, and they spray fine. The only drawback is you have to mix certain colors to get what you want. Nothing wrong there, just less convenience than Vallejo. However, this is why we’ve got AK Real Colors. Not used them myself, but all I’ve ever heard is that they are a dream come true!
Now, I’m not saying switch paints; if you like Vallejo, stick with it! I’m keeping my arsenal in case I need it for a model (and of course for my figure painting needs), but for my armor builds I am going to slowly make the switch to Tamiya.
HTH! 
Edit: I went and counted, I have about 100 bottles of Vallejo, 80 bottles of paints by Scale75, and 20 bottles of AK acrylics. This is compared to 15 bottles of Tamiya. The switch is long and arduous, but I think it’s worth it.
What Matt said.
Fully endorsed by this Filosophyical Fanatic of Floquil Forever Faction
"Vallejo, nice paint for hairbrushing is a hassle airbrushing.
The best paints typically thin with Mr.Color Leveling Thinner, then prove worthy of becoming an airbrush friendly airborne aerosol in my 47 years of airbrush experience with hobby paints.
I woke up early and ran the airbrush at 6:30am.
What you see is my best effort at Africa camouflage with the needle shroud removed. The Jagdpanther is only halfway primed because the airbrush was behaving very badly and my back gave out.
I will consider purchasing a new airbrush, new needle, new nozzle, and/or new paints.
Doug, what airbrush do you have now?
I use an Iwata Eclipse HP SBS.
If water is forced through the nozzle using an eye dropper, it shoots to one side. The airbrush sprays to the side as well. This problem began two days ago.
In the past, this sort of thing always resulted from a clog. If it is clogged, the problem paint resisted multiple cleanings. The next step is to fully immerse the nozzle and color cup in alcohol.
Even if the current problem is fixed, the airbrush still cannot spray camouflage. The airbrush cannot do anything like what people in videos demonstrate.
My other airbrush is an Aztek A470. It is even worse. I have not used the Aztek since purchasing the Iwata in 2009.
Doug, do you have any larger size needles for the Iwata? I’d swap out the needle and test some other paint through it.
That Iwata should shoot flawlessly. I didn’t know the model and that it had a floating nozzle. The needle may not be bent. You may have no reason to get a new airbrush. That is an excellent airbrush. The nozzle has dried paint in it. It needs soaking in something stronger than alcohol. You need to go to the hardware store or Home Depot and get some lacquer thinner. Soak the nozzle in lacquer thinner overnight and shake it around. I bet big bits of dried paint come out. Put the airbrush together and spray lacquer thinner through it in a well ventilated space. Make sure the airbrush is performing perfectly.
Get some Tamiya or Real Colors paint and some Mr. Color Leveling Thinner. Don’t use the hardware store thinner to thin paint - it’s too hot. Only use it to clean the airbrush and save the Mr. Color to only thin paint.
Mix the Tamiya\Real Color 50\50 with the Mr. Color in a separate jar and give it a good shake. Pour it in your airbrush and prepare to be amazed. Your airbrush can be dialed down to 5 PSI and do pencil lines. I swear it. The end of your airbrush frustration is near.
Today started with another early morning paint session.
Priming went fairly well. Painting tracks and tow cables went okay. I normally wait 24 hours between priming and painting. Trying something new, once all primer was dry to the touch, a base coat of paint was applied. Well, part of a base coat was applied. My back gave out after two hours so that is it for today.
Vallejo Model Air Panzer Dunkelgelb is the Kursk variant and probably not appropriate for Normandy Jagdpanthers. Maybe I can mix something more tan.
Cast texture needs some sanding.
Construction of the Dragon Jagdpanzer G1 approaches completion. When tape was removed, the hull did not pop open. Yay. When dismounting the tracks, nothing broke. Yay, again. Rather than use the late Panther A exhaust configuration provided, my model uses an early Panther G arrangement. Maybe that is right. Maybe it is wrong.
…
@SSGToms Thank you for all the advice, Matt. For health reasons, it is water based acrylic paints or nothing. Also, lacquer based paints and lacquer thinner are illegal in California. Isopropyl alcohol very quickly dissolves Badger primer and Vallejo paint so I will try that.
Based on comments made in these forums a few months ago, I am considering purchasing a new airbrush.
@BattleScaleCollectic Hey, Jack. My airbrush uses a .35 needle. A .5 needle will not fit. One reason I am considering the airbrush linked above is the ability to switch nozzles and needles.
Doug, have you thought about getting a replacement needle for your Iwata first? I think they usually go around $15. I recently got a Master & Gaahleri AB with multiple needles but haven’t tested them out yet. Not planning on replacing my Iwata, just needed larger patterns for bigger parts.
Another early start. Another day of frustration.
Last night, I took apart my airbrush and left most of the parts soaking in a tub of alcohol. This morning, I started with a cleaning, then mixed up the first color of the day and started spraying. The airbrush clogged after a few seconds. I tore down and cleaned the airbrush. It clogged after a few seconds. This was repeated 5 times.
For cleaning number 6, I removed the trigger assembly and cleaned through the entire body. A wire brush brought out a very small amount of black primer.
The airbrush is still clogged but now behaves differently. After two hours, I pulled it apart, dropped all the parts in a tub, and gave up.
Back in 2010, I quit building models because of unrelenting airbrush problems. I have never experienced an airbrush that sprays like the ones in YouTube videos.
Dunno. Considering quitting for good. I am not having fun, not getting better, and not producing anything approaching a decent model. In 4.25 months, spending 40 hours a week trying, I have not completed a single model. I am almost out of ideas and patience.
that sucks. I suspect you need to try another line of paints. I really like AMMO Acyclics.
I also think you have junk in the AB alcohol just isn’t cleaning out.
@SSGToms I followed your advice and soaked the airbrush in ‘something slightly stronger than alcohol’ for a few hours. This whole affair is very much a comedy of errors. When removing the parts from the tub, one glove tore and ‘something slightly stronger than alcohol’ ended up all over my right hand, which now has a rather pronounced rash–basically what I really wanted to avoid. I laughed when it happened because of course it happened.
Airbrush advice is another funny thing. One person will say, “Do THIS and all your problem will be solved.” After doing THIS and it not working, I will come across another person who says, “Never do THIS! Do THAT and it will solve all your problems.” Okay. So I do THAT and it does not work. The third guys says, “Never do THIS or THAT. To solve the problem do SOMETHING ELSE.”
Please understand, I find this years long fiasco funny. I could write a book discussing all the ways I have tried and failed to properly operate an airbrush and compressor. Annoying. Frustrating. Full of despair. But funny.
After the last series of cleanings, my airbursh is now blowing bubbles into the color cup at certain trigger positions. That is a weird new one! Once again reading what some guy on the internet says about airbrushes and bubbles, it is often a sign of…a cracked nozzle.
Okay. Now we are getting somewhere. Three different things are now pointing at a problem nozzle. Therefore…
@BattleScaleCollectic Thank you for your advice, Jack. I just ordered a new needle and a new nozzle. If those do not work, I will order the cheap replacement airbrush. If that does not work, I am thinking about setting all my models on fire. That was a joke. Probably.
If the new needle, new nozzle, and new airbrush do not work, I will start looking at other acrylic paint lines.
After this all went down, I went outside and shot baskets for a few hours. That helped.
If you go down that route, I am still liking this one.
Hey, Ryan. That is the exact same one I am considering. If I recall correctly, a few members of this forum tried G233s with very positive results.
My Aztek and Iwata SBS are both side loaders. Side loaders have a very long paint path allowing clogs to occur in more places. EVERYONE on YouTube uses a gravity feed brush. EVERYONE. They do not have problems. I do. Constantly.
A few days ago, I guy in a video suggested painting without the needle protection shroud. Okay. I gave it a try. It was definitely different. In the process, I probably bonked the unprotected needle against the bottom of my airbrush station, cracking the nozzle. This would explain why the nozzle began shooting to the side right after that session. I constantly lay my airbrush on its side. It explains why the Iwata is now back feeding air bubbles at certain trigger positions. It explains why the nozzle now clogs almost instantly.
If that is right, the new needle and nozzle will completely fix the Iwata. The ‘something stronger than alcohol’ bath should have removed any remaining gunk. That will leave me with one good airbrush.
Having a second, gravity feed airbrush would allow me to test many things. Maybe a side feed airbrush was the major problem all along. Maybe the 0.35 noddle is the problem. Maybe alternating between primer and paint is the problem. Maybe not having a trigger stop is the problem.
Dunno. Having watched many hours of YouTube painting videos, it is hard not to conclude that the problem lies entirely within me. Many of those artists use acrylic paints, Vallejo paints, without any major issues. But they ALL use gravity feed airbrushes.
Sorry for being a downer. I want to make models but this 25 year airbrush opera is extremely frustrating.
I understand, I have a love hate relationship with the airbrush. I do also have a side loader, I don’t recall that being an issue with my Vallejo and Tamiya paints. I have replaced the side cup with a larger Aztek cup. To me the ratio of paint, thinner and retarder is the key for in your house. It’s different for everyone. The needle size for me was a big difference with primers. The Master with .5 fixed that issue for me.
The trigger stop can be helpful for consistent paint application but that can be learned without one.
Have you tried mechanically mixing the vallejo paint in the bottle? After having many issues with Vallejo this year, i tried it out.
I have a small, battery powered engraver from Harbor Freight.
I also happened to have a piece of brass rod about the same diameter of the engraving bit and bent up small piece that fits the bottle. I have also cleaned the paint from the bottle nozzles dry or not.
My Vallejo paints are a good 5 years old and i have never mechanically mixed any of my paints.
So it did make a difference.
Also make sure your AB spray nozzle is not cracked.
@Tank_1812 I’ve been trying every few years since 1999. Airbrushes do not compute. I am aware that some people really like side loaders and use them well. That is more evidence the problem lies entirely within me.
With regards the trigger stop, I very probably lack the manual dexterity required to master trigger control without assistance. I really struggle maintaining the trigger in the same place for more than a few seconds.
@petro My Vallejo paints were all purchased within the last two years. I made the switch last May, right around Post 24 of this journal. I have experienced severe clogging on a number of occasions when using Vallejo Model Color paints because some dried paint entered the system. Thorough mixing definitely helps and thank you for suggesting the engraver!
As for the airbrush nozzle, it must be cracked. I cannot see the crack but it must be there. I ordered a new needle and nozzle earlier today.