Decaling: Setting Solutions & Clear coats.

I find I don't usually need a setting solution. As long as the decals are going over a gloss surface, you should be fine. I glosscote the whole aircraft before decaling, apply the decals, let them dry a few hours, then spray it overall with your final glosscote or satin cote. I use Testor's model master from a rattle-can (spray can) for my topcoats. I have had no issues, juts be sure you put the initial coat over the decals on lightly, too much and it can react with them and "eat" them. As to the brushing, assuming you used Testors dulcote from the bottle, as long as you only run the brush over then once, then let it dry without touching it, it should'nt be an issue. You can run into problems if you run the brush over them again when the dullcote is on them and smear the decal.

Good luck.