Get a Preval sprayer from your local hardware store and you can use automotive grade primers and paints.

http://www.preval.com/

If you do use rattle cans beware of possible color variations from one can to the next. It's all too easy to end up with a cylinder head, intake, etc that won't quite match the rest of the engine based on where you were at when you switched to a new can of paint. The Mopar Performance Hemi orange cans I bought many years ago were all over the place.