My opinion based on discussions with the PPG guy and painting various projects over the past 25 years.
Paint needs "tooth" so it wont come off when you hit it with the hose when washing. I generally dry sand using the DA and 280 - 320 grit paper. Then apply color and clear. If I did it right, the clear is near perfect (happens only 3 out of 10 times). If I sneezed when applying, then I can wet sand and buff the clear. If you sneeze during the color coat, then wait 4 hours and wet sand and tack prior to spraying clear.
Scott
