[A8ked]

I painted my front bumper grills and side vent grills about a year ago and they have held up well so far... I used a paint that was made for use on plastic. Apparently it bonds to/with the plastic.
For the side vents I just removed and painted the grill inserts, not the outer trim. I painted the front grills while I had the bumper off to clean the radiators. Its simple enough to remove and repaint them if they start to look rough in the future.