The first thing you're going to want to do is get a brass bristle brush and remove the surface rust.
Then, what I've used, is Rustoleum High Heat Grill paint. I think they only make it in black. Wally World is where I found this stuff. I've read here that others have had success with High Heat Engine Enamel paint. Made by Dupli-color I think. O'Reilly or Autozone should carry this. Both are aerosol/spray can variety. Just tape off the areas that you don't want to paint and Voila! Hope this helps.