I agree with mirwin. I experimented many years ago with applying paint to pastic coverings. That was back when evryone said it couldn't be done. I found that epoxy and petroleum based paints will adhere very well using mirwin's method. But, I've never been able to get a water based paint to stick. I've never tried putting water based over automotive primer sprayed on the covering. I think it might work, but I've always just used the same brand of paint for the color as the primer. I've had my best results with Rustoleum. You can buy it in a non-spray can and mix the colors to get what you want. It will need a little thinner to get it to spray well. Practice on a scrap panel to get everything figured out. Follow mirwin's advice about surface prep and cleaning. That's the secret!

Paul