AMMO Extra Thin Cement, is a great glue for your plastic model kits, it works by melting two parts together to create a strong bond between the plastic compo...
Painting it on like that from the visible side could leave marks on the visible plastic.
I bought a gallon of ethyl acetate instead …
I have always done it this way w/no issues.
What surprises me is that they did a video to explain how to use it. I always thought it was pretty intuitive.
One has to generate content of products especially for new comers to the hobby that might have any mentors.
Maybe the stuff you use is less potent than my 95% strength ethyl acetate 
It is intuitive. The AK and Mig guys have become internet influencers as much as modelers. They need wide-eyed followers. It’s not to get you to use extra-thin cement, it’s to get you to use their extra thin cement.
Tamiya extra-thin quick setting is the best stuff going in my book.
Plus one on this response - next promo video may well be “ How to open your model’s box “ …
I have to be honest, as a modeler coming back into the hobby after many years away, I learned about the capillary effect of extra thin from some Youtube videos. Its sometimes hard to remember that new people just don’t know what comes easy to a veteran builder.
Some of them boxes are dang hard to open, there is zero play between the lid and the bottom tray
And after fighting it for a while you realize that you may have taken the outer cellophane off the box but the box is still held together by tape 
This type of box does not need tape to hold it closed. The friction between lid and tray is more than enough. The slightest angle between lid and tray locks them in place
I hear you. I had to open both ends of the cover box on the Zvezda 1/72 Yak-130 to push the inner box out the other side. 
