I own a powder coating shop so this is up my alley.lol
I would use wetdry with all the paper.
What exactly are you cleaning up?
After all that work is done I'd zoop seal it. It will keep the nastys from coming back.
U can also have it clear powder coated but that will drop alittle of the shine off.
Zoop seal is best but it costs a good bit to so make sure u have enough parts to zoop before using it. U can keep zoop good for about a week in the fridge. Covered of course
doing the alternator right now, so it is or isn't ok to use the regular(non wetdry ) sand paper? I have some handy and want to get started... i'll use wet dry from 220-400 but even autozone didn't have wetdry for 220-80