As in take them straight back to raw plastic? Or black paint?
If they're already plastic and you want to paint them.
Remove them
Clean them thoroughly, I mean thoroughly.
Hit them with Wax and Grease remover.
Paint with Plastic Primer - follow cans instructions.
Let dry.
I hit it with wax and grease again because I wanted to be sure.
Paint with colour - few coats.
Let dry, harden.
Light wet sand to flatten.
Polish.
My paints only white so I don't have a clear coat, but I'm not sure about the black.