clean and degrease
prime with rustoleum self etching primer
coat of rustoleum black
top it off with more black and clear coat or rustoleum bed liner
This is assuming you want to paint it black...
For colors I have been pretty happy with the rustoleum hammered finish paint. Just stay away from the "paint and primer in one" version. My LJ parts are all the rustoleum hammered and have turned out good. Just realize it will have texture.
I have jeeps. I do shit to them.