Todd@RUPES
Just a regular guy
If you watch old episodes of American Hotrod, Boyd's guys would start out at 800 grit, even on a car painted by Charlie Hutton (if you dont know who that is, Google him). Granted thats on a fresh repaint and not factory clear, but its still the same concept.
I know of one painter in Southern California that blocks each coat with 600 grit until the final coat which is blocked with 800 first as well. Then the car is parked in the desert for at least 6 months before being blocked once again with 800 grit.
His paint jobs cost upwards of 60k and there is a LONG waiting list to get him.