I had tried to "paint" hard plastic back in the day and never had much luck. recently I have used some of the paints specially formulated for plastic on some motorcycle parts with good results.
when I wanted to recondition some of the plastic in my '01 boxster I decided to give the carbon fiber vinyl a try. after a bit of trial and error I finally got the hang of it. did the door storage bin cover/armrest, the door release covers and the gear shift, which had been rubbed completely paint free:
https://flic.kr/s/aHsjVthyPk