I am curious about the other modelers approach with this thing.
See, I am a cheapskate at heart, and I really hate wasting materiel when there’s no real gain involved so I tend to avoid painting/weathering everything that is not going to be visible.
For example, on my ISU 152 I didn’t weathered the bottom parts of the treads that are hidden by the floor. I just touched the visible parts.
Depends on the model and the mindset I have at the time.
Tracks get an all around work up because I leave them off until the bitter end and never know which way they’ll end up.
I’ll base coat the bottoms of my vehicles and use them as test beds for washes and weathering and such. They’re an ungodly mess when I’m done, but you can’t see them.
Interiors I’m hit and miss on. If there’s going to be a couple open hatches then I’ll at least base and wash depending on the detail visible. If they’re barren inside and I’m buttoning everything up then it’s bare plastic all the way.
Im gonna try to answer this is politely and unbiased as possible. 
Always paint and weather EVERYTHING. You’re not wasting any material if its going into improving your model.
At shows, the judges will scour over your model hoping you did something like that… they find something: minus points.
After judging the first time I can firmly say I am going to spend much more time weathering the bottoms and hard to see places of my builds, as I lost 5. points for the bottom of one if my builds being only base painted. Do you think the insides of wheels don’t need to be painted? WRONG! A judge’s flashlight sees all.
Moral of the story? Try not to be a cheapstake!
If they can’t be seen when the model is complete, I don’t worry about them. If we are talking about a model with an interior where, probably some will still be hidden, I will still build pretty much all of the interior. I am just a glutton for punishment with full interiors.
I don’t build for contest judges, so I don’t give a damn if they see it or not.
Hehe, but NOBODY is going to handle my models, you can count on that! 
At worst, it could be some toddler while I am not looking, and that will mean a whole new set of problems!!!
There are merits to your points.
There is also things one can do help yourself, bases and terrain can hide lots of sins and prevent most judges from finding issues. 
I don’t compete either but that said having a judges mindset does help one improve one’s skills. You look at the subject differently. The biggest jump is basic construction and it goes from there. That is for both IPMS and AMPS style of judging.
That also depends on what a modeler wants from the hobby. We all enjoy it differently, not one way right or wrong.
I would at minimum recommend painting it all, even if it’s just a black “primer” coat (doesn’t have to primer paint could be just flat black). Nothing worse then having a painted and weathered model and a little tan or grey piece showing through you can’t reach.
Weathering is up to you, where and how much.
Well honestly it’s all up to you but that what I would as do at minimum.
Based on the judges’ comments from when I have competed, most have no idea what they are looking at (unless it is a WWII German vehicle) anyways. I build for myself and base my weathering on actual vehicles I have served on. I don’t worry about what they have to say.
That doesn’t make sense to me. When I judges decades ago, you didn’t have to know the subject. In fact at one show (Houston?) they preferred that you didn’t know that category well. It’s all based on construction and finish. As primarily an armor modeler I found myself judging aircraft more than once. No one ever complained.
If it can’t be seen on the finished model, and it isn’t structurally necessary, it doesn’t get included in the build, let alone painted. You never know when the bits might come in useful, even if it’s only greebling a SciFi/Fantasy scratchbuild.
Cheers,
M
Exactly. Return roller wheels come in handy for all sorts of things.
I am in this camp. I build for me, no one else. 90% of the time, if it cant be seen then it wont be weathered or painted. A painted radio or breach block in a tank turret with hatches closed will never be seen and honestly wont do much to improve my modelling/painting skills.
I have tanks missing upper runs of tracks because they are completely hidden and would be a pain to install post build. Planes missing inner fuselage detail because it sits behind a bulkhead and cannot be seen. Hanger details on ships missing/unpainted because its impossible to see due to the angle of how you would look at it.
On a personal level I am with Rory and Gino, but at the same time everyone else has made valid points in one way or another.
I only build for me and no one else. I look at other people’s builds here and some are truly amazing, and that includes everyone who has posted in this thread. I genuinely know I get more pleasure and enjoyment from my peers here when they comment on my builds than I would get if I ever showed or even won a medal, and that’s the honest truth guys.
I have at times painted every single piece on a kit only to think after I’d finished it… Why did I bother to paint that bit inside that is literally never going to see the light of day…
Some people like to do the whole thing inside and out and that is totally fine as this is all about individuality and what makes you happy.
On my CVRT Striker build I went all out and put in 120%… It was my long term vehicle as a commander and it deserved it … The Chieftain Stillbrew I’m doing was a ride of mine, but not on such a personal level hence the next image.
The tracks in front are as they will be. The top run will not be getting any paint other than the primer. It’s going to be hidden behind boz plates for eternity. Same as the return rollers…
It’s not even me being totally lazy… Painting them seems pointless…
End of the day guys … Whatever makes you happy 
That’s it in a nutshell.
Ken
Very often since it’s usually easier than endless test fitting to check sight lines and views to be sure that everything that can be seen has been painted to the same standard as the rest of the model. I’d rather spend a little extra time painting parts than discover later that I’ve missed something.
However, I’m not beyond simply painting large areas flat black and then only finish and detailing painting the much smaller areas that are visible through the hatches.
Just depends.
Ultimately it’s the modelers choice of course.
I paint all the exterior surfaces, back side of road wheels, under the side skirts or bottom of the tank, all of it. For me it’s 2nd rate effort unless I paint all of it.
Starting on the bottom of the tank model is a great “warm up” if one hasn’t painted in a few weeks. I can make sure all is in order with paint mix, air pressure, airbrush etc before working on any area exposed to view. It’s the ideal area to experiment with shade and fade etc. Using 15 cents worth of paint on the bottom has probably saved models from a compromised paint job.
Wasting paint on bottom of tank argument, is at best a trivial concern when painting a $50 to $80 model with 40 to 120 hours of build time. Worry over maybe 15 cents worth of paint? Not me.
Mix 1 or 2cc’s of paint for the airbrush at a time typically. Basically little no waste painting the bottom. It has very little impact on my paint usage. With a good gravity feed airbrush one can mix drop by drop if needed.
I still use Floquil RailRoad Weathered Black that costs $50+ for 1oz bottle on Ebay these days, I’m definitely on point with conservation of precious vintage paints 
and still paint the bottom of the model.
Despite being basically “retired” from building for contests or judges, I still strive to maintain building and painting to IPMS contest model standard. Exposed unpainted plastic is on the same level as failing to remove exterior punch marks on parts to my point of view.
YMMV
I know that isn’t for everyone but that’s my thought process.
Meh… if a job’s worth doing, its worth doing properly.
Paint everything, weather what would be weathered.
Point is, it doesn’t matter if nobody is ever going to see it - YOU know its there. My personal pride would prevent me from doing a half-baked job. Its not a waste of material.
No I don’t, what’s the point of weathering the underside of a turret if you won’t see it?
No one knows it’s there except me. But I admit…I paint everything.
