[Precision]

I was wondering if someone could school me on painting car plastic.

What sandpaper works best to prep? I don't know what grit and I need to sand off chrome from kidney grilles and silver plastic paint from fog light fins and mesh. Does it matter? I used 400 grit and it took me forever to get anything off.

For paint I was using a black enamel paint, it worked good the initial coats, I missed a tiny spot and it drove me nuts and I figured I'd hit it one more time but this was hours later and all it did was that wrinkle crinkle dry...

Primer? Is it necessary for plastic? I want to do a good job but it doesn't have to be show room. I've had zero luck getting a smooth finish out of this enamel paint on my kidney grill, I'm thinking I need to sand it down to remove all the paint and do it over. Will primer allow it to dry smooth and stick? I'm doing this in my garage.

Any other help would be great. Suggestions on materials would be nice too.