RE: Fuel proofing inside of fuselage.
I tried spray cans once upon a time.
It's like almost everything in our hobby. It's a technique that has to be learned.
Some cans produce a HUGE amount of fog. I was outside and still fogged my arm above the rubber glove (that went halfway up my forearm). The fog got on the outside of the plane. It went out the hole in the firewall and wafted out the wing saddle opening.
I was doing a 40-60 size fuselage and that meant that the spray nozzle was only inches from the target. I didn't care a bit about runs, but at that distance you're going to get LOTS of them. Turns out you're going to discover ANY opening in every joint that gets sprayed. The firewall leaked in a couple of places and the covering around the nose showed paint inside it along one seam. (Taught me a lesson about the "quality" of ARF construction) The runs inside the fuselage sometimes become dripping paint on the outside, or inside the outside monokote.
I figure if I ever do it again, I'm going to rig a remote button pusher and a way to hold the can on the end of a stick. Either that or use a paint color that matches the shirt I plan to wear for the next week or so. I'm also going to mask off the whole outside of the model.
I figure there is a way to do it. I'll use my airbrush, the very smallest one.
And there still will be a bit of a problem. Getting the "back inside" of the bulkheads is tough. Getting the spray can (or anything) pointing "back toward you" is tough because it's so cramped. So you got to rely on overspray and those runs. After throwing the can as far as I could, I started tilting the model around to get the runs to backfill the hidden sides of the bulkheads. Got no idea if they needed it or not, nor if tilting the flood did any good.
Like I said, it's a technique. I'd suggest that your question is an excellent one, because I'm sure that there are certain brands of cans that spray the kind of spray needed for the task. I just didn't find it. I got the shortest can I could buy, knowing the confines of the fuselage would make a long can worthless. And that short can PUMPED out the paint. And holding a can in your hand sort of uses up all the spare room you got.
So the important detail is: which brand? and that's actually which can?
But then, I bet the 20% models are no problem.