RE: painting mold before layup
Painting the mold with regular layup and no vacuum will work but be sure not to have any void spaces under it from bubbles which is really hard to keep bubbles out in a wet layup.
I would use some thickened epoxy (thicken with microballoons or silica is even better) and brush it in the cowl after your paint has flashed off but before it's cured. Let the surface coat of thickened epoxy setup a bit so it's still tacky but does not leave any brush stokes if you run a brush across it. Then layup your fiberglass and the surface coat should keep any air bubbles from showing through the paint. The thickened epoxy will be thick enough not to run but not so thick it clumps up. Like warm creamy peanut butter. You just need a thin coat.
For paint on nitro models I'd only use Klasskote and use their primer. For gas I've seen just about anything including Behr house paint. If it's going to get a lot of use I'd still go with Klasskote on the gas planes. I have a big gas plane that has house paint but I don't use it that much. With KK paint you will wait about 4-12 hours before you start your surface coat of thickened epoxy so it has time to cure enough so it isn't damaged when you brush in the surface coat of epoxy. You could do it a little sooner depending on temperature and humidity...just press on it and see if it leaves a thumb print. If it does, give it a bit more time. I don't paint in the mold so from what I've seen with painting with KK this should work but I'm not going to say that any paint will bond properly with uncured epoxy.
I'm not a big fan of painting in the mold because if there's a seam you have to sand it down and repaint anyway. Even if you just prime the mold I would worry that the release agents will get in the primer and the paint won't stick. I still don't know why guys do it because it seems like it's more work in the end. Unless they just like seeing that pretty part come out of the mold. If your mold is perfect you can get a nicely blended multi-color paint scheme but you ruin it if there is a seem in the mold that has to be sanded and repainted.
I've seen guys use rattle can primer and they prime the mold and let it cure, sometimes for days, and their paint and primer is always peeling off. It may be the quality of the product they are using, or the dissimilar materials like polyester and epoxy, I don't know.
Good luck and post some pictures.
Tim