Give it a good sanding first with a medium-rough paper, get off all the gloss and some of the base paint too, then clean it really well with some acetone. I'd suggest Krylon Fusion, since it's supposed to bond well to plastics and it's pretty good paint, get it in glossy or whatever you want and also some clear coat. You're going to want to take your time when painting if you want it to work well, lots of very thin coats with a some light sanding between. I'd say after 5-10 thin coats, whatever it takes to give it a smooth solid look, repeat with a few more coats of clear doing the same thing, thin coat and sand, repeat. This should give your a really solid paintjob that'll hold up about as well as you can do at home.