Nathans_dad,
When I painted one of my tactical shot guns, using the Dura Coat finish, I purchased an airbrush and a small compressor. It worked perfectly for what I was doing, meaning, I didn't want to lay down lots of paint.
I have the Fusion F1 Air Compressor like this:
http://www.dickblick.com/zz251/28/
I have teh Paasch Model H airbrush, like this:
http://www.dickblick.com/zz250/05b/
I hope that helps.
Bill