here is my theory.....

if you paint your your black plastic molding without primer, when the paint chirp, it is not that obvious as w/ primer.


so just stick w/ sanding and spray a layer of paint over it.

anyone here agree or disagree?

 

try something not as thick as primer then..

there's a clear basecoat you can get, it's thiner, clear and it's more flexible than primer.

well, think, when your paint peel off, it will not come out as nice as your want.
primer or not, you shoulg strip everythign down to plastic before repaint it.

 

if you dont prime, the paint wont adhear as well. You may encourage cracking and chipping otherwise.

Just a thought.

A better option is to use a high grade clearcoat. I did on my ITR lip and rear bumper. You can see a difference.