Well, since its plastic, your going to need to sand it down, with some rough sand paper like 100 grit then down to something fine like 220. Spray on some Primer, then the paint, and perhaps a clear coat high gloss finish, if thats the finish you are trying to accomplish. Do several light coats of paint instead of one thick, it'll look much better, trust me. And make sure you give it AMPLE time to dry, like 12 hours before really messing with it. Read instructions on the spray paint can for exactly how long, but trust me, i've messed up i don't know how many paint jobs on things because I was too impatient and ruined all my time.
'89 SSE - GX3 -190k, 155k on body - Back for another ride.