When did glosscoating, prior to decals, become an absolute, hard and fast rule? It’s a good idea, sure, but not always necessary.
With good decals, like cartograf, I’ve never had to gloss. With crappy decals, like from airfix, no amount of gloss is going to get those things to lay down, correctly.
Depending on the quality of the decal, you can almost always get away with a bit of decal set and solution. Brush on a bit of micro-set, place the decal and let dry for a few minutes. Absorb the excess with a q-tip. Then apply some micro-sol over the decal and it will pull it into and over all the detail, without the need of a glosscoat.
If you can’t get micro-sol/set, you can use a little puddle of Future where you want the decal to go. This is localized glosscoating and reduces the chances of spraying mishaps, like overspray or orange-peeling.
I’ve never been a fan of the “absolutes” when it comes to modeling. The great thing about this hobby is that it allows for experimentation with different techniques.
If you have a really thick decal that won’t settle down, no matter what you do, you can use a sparing amount of liquid solvent, over the top. Brush on a thin coat, very quickly. You only have a few seconds before the solvent will make the decal too soft to work with.
If you have to hand-brush the camo, Testors is superior to Tamiya. Thin it a bit so that you don’t get brush strokes. Free handing is fairly easy - draw the camo on first, using light pressure with a pencil. Then use a liner brush to paint the outline and a wide brush to fill it in. It’s just a technique that takes practice - particularly the thinning ratio.
-Fred