I think most people would recommend that you get it sandblasted and Duracoated or Parkerized instead of just spray-bombing it. I think the main issue with the homebrew finishes is that not all of them will hold up to the gun cleaners and oils and such. I've got a front clamp-on sling mount from my shotgun that I'm going to try painting myself, but I've already stripped off the bluing, and it'll just be a test piece. If you've got a piece you don't mind playing with (like a sling mount), then you could pull it off and try sanding it a bit to give the paint something to stick to, then giving it a shot of Armacoat. I believe there are a couple dealers on the site that'll happily sell you a can of the stuff in the colour of your choosing. In any event, I think it's all about preparation... whoever sells Armacoat (or whatever finish you choose) might be able to give you a better idea of what's required.