you can use a plastic primer:
then use whatever you want, i just opted to go straight for the 'plastic paint'
Krylon: Products: Fusion for Plastic®
Royal Blue Spray Paint by Valspar Corp - 400.0012009.076 - More Spray paint at doitbest.com
works well, but you have to mind the drips... i just hit em with a little sandpaper and recoat. they do make an attachment for the can that supposedly helps cut down on over coating on the 'turn-around' if you will, but i didnt pony up the four bucks to try it.
Air Spray Guns - Paint Sprayers - Ace Hardware
edit:i did get a small roller to attempt to help application, and would not reccomend that at all (for spray), it tended to leave a 'dimpled' look--which may have resulted from the nature of the paint. that plastic paint almost seems to have cotton candy-ish fibers in it.