As in the title not wanting to key a car for some sort of revenge plot.

What sort of grade of wet and dry would someone recommend 180 to start and then 600 to finish?

The car is going from silver to matte black if it makes much difference so the quality of finish doesn’t need to be that great.

Probably not this.

If you are changing colour and not doing and repairs. Don’t go any coarser than p800 or p1000 dependant on paint used. Or use something like mirka mirlon scotchbrite. I use grey or the fine one to key orginal paint work before painting or sometimes 3m trizact 3000

Make sure you use some panel wipe too.

I run http://www.expresscarbodywork.com

If you have a questions just ask.