Originally Posted by BoilerUpXFire
It all depends on how rough the starting surface is and how good you want it to look. For most parts intended to be finished and painted, a 320 grit SP will marr the surface terribly and require you to do much more work. I would start with at least a 600 and work to a 3K, but again, it depends on how good the original finish is....
the surface is real smooth but they whant you to use epoxy primer wich is heavy