I am using...i forget, I think 200 but it might be 120...no I think it is 200.
Start with 80 or 100. Sand until you just start seeing plastic showing through in spots.
Then switch to 150 or 180. Use a block or hand pad to keep things flat. You don't need to get
every bit of paint off.
All the pieces will be getting primed and the scratches will get filled.