I would like to add, that dont go buy the little cans of spray paint at your after market parts stores, I really dont think that would hold up, but that is only my opinion. My wife is a airbrush pro hobbyists, and we get our paint from real auto paint strores such as DuPont etc. But our base primer is a serious high temp industrial prime and oh yeah, only oil base.
I use my shotgun for all different types of hunting and down here in south Louisana, the weather can get very ugly in a heart beat, so your paint has to be tough. Tougher than your hunting.
Just remember to have avery clean start, and no matter what kind of pattern you paint on it, it is going to hold up. My wife is not a professional expert, but she did good on matching the factory stock camo pattern. She mixes colors and starts doing her thing. Me,I am just the laborer on the job, you know, preparing the surface for her to paint. Hope all of this helps, and happy hunting. Of course you can always go another route and buy the camo tape from Cabelas or something like that. Let me know how your gun turns out.
Joe