im putting paint thinner on my mugen lip to take it down to its bare plastic again...i know to clean it hella good with soap and water and let it dry, but my question is: before i apply the oem trim paint from autozone to give it that black look like side skirts do i need to put a primer first?

 

It would help the paint stick to that type of plastic if you did primer it and then sand it again and repeat your cleaning steps.