I depends on what year Corvette you're working on.
C1's thru C3's have most likely been repainted, so do a test panel.
Early C4's have very workable, easy to polish paint and M205 should be more than adequate.
Late C4's, C5's and C6's have that rock-hard "diamond clearcoat". It is a true pain in the ........ to work with!
My best experience has been with M105/M205 and a rotary. With a Random Orbit, even a powerful one, like Griots, it can take 12 hours to polish a late model Vette.
I resisted rotary polishers for a long time, but with newer Vettes it's almost a necessity.