With aerosol paint, I would think the color coats would be much thinner than "automotive" paint, therefore making sanding through more problematic. Personally I wouldn't sand the color coat with anything coarser than 600 or 800 grit.

IMHO, I recommend either Eastwood or Spraymax two-part urethane clear for an excellent gloss. I use 2-3 cans with one tack coat and then one continous wet coat until all dry coat is eliminated and I have no clear leftover. I have yet to put a run in the clear. I always spray in warm to hot weather. The Spraymax flows out slick.