i bought a brand new ground effects piece to replace the broken one on my car and plan to paint this weekend. right now, it has no paint, just that gray plastic look, so im gonna paint it before i put it on the car. i also wanted to redo the nose because of the rock chips and what not from the road.

what is the best way to go about painting these, being that they are plastic and not metal. for the nose, should i sand it, or just spray right over it? primer or no primer for either? would i need a clear coat to go on top of the paint?

these are the main things im worried about. any other tips and tricks you can share would be greatly appreciated as well.