If you are painting over existing/repaired factory coat, scuff everything including your repair areas with 320-400 grit, and that will be adequate. This is the advice my paint shop gave me, and I have sanded the entire car by hand. The door edges and jambs that I painted turned out perfect - no sanding swirls or marks at all. The rest of the car needs painted, but it's off to a good start. These cars are not massively large, so hand sanding is a reasonable and achievable option.
Chris