I decided to paint the plastic trim panel under the deck lid. I used a special Plastics primer from a company called SEM as the plastic is polypropalene. I sprayed it with a spray can and it came out crap so I want to redo it with a spray gun. I have never done this before so the questions I have are, in order to repray it do I have to sand it down to the plastic and re prime it or is it enough to give the panel a slight sanding and repaint. Will new paint stick okay to the old paint or without using a primer again will it crack?

Thanks.

 

I never painted plastic like that, but from my painting experience if you have 1 bad coat of paint, it won't ever come out right. You are always better off sanding old paint off and starting over.