I am planning to use an airbrush to paint my plugs. What kind of paint do you guys use when using an airbrush?

Createx is what I use.

I like a high quality oil based pain, like rustolium or Krylon. But not the stuff in spray-paint cans. I like to do my own tinting. Buy the tint base and some primary colors and tint to your liking. I like to have aluminum paint on hand to creat my own mettalics too.