Here is what I used to paint the chrome trim, door handles, and plastic parts on my Brick with great results. I first scuffed the plastic with a Scotch Brite pad and sanded the metal with 220 grit on a D/A sander. I then applied Bulldog adhesion promoter to the surfaces per manufacturers instructions. Next step, just paint as normal. I got the Bulldog from the local PPG paint supplier I use. E-mail me for a pic of the results. Later, Paul

The other ways work too. But this way you avoid mixing small amount of primer.