Brownell's sells Gun-Kote in rattle cans, though I haven't used it. It needs to be baked, I have a toaster oven which I have used for baking guns, works well.
Duracoat needs an air brush, but does not have to bake. Not quite as durable, but it does come in lots of pretty colors.
Your RIA should already have a parkerized finish, which is a good base coat for paint. It needs to be thoroughly degreased prior to painting, however.
Before I moved up to the dedicated firearm paints, (they really aren't, they are just marketed that way), I experimented with both engine and header paint from my local auto parts store. Duplicolor engine paint works sort of well, and I used VHT black header paint on a .22 Smith that was really badly pitted. Looks fairly decent now, and I am tempted to try it again on a parkerized finish. This is a really low dollar approach, however.