Even though my car sits in a carport, I dusted it off with a CCD and gave it a thorough (but gentle) wipedown with QD. This seems to work okay and the CCD takes care of most of the dust. I can tell if I did a good job at this or not when I'm applying because the dust I missed gets picked up on the applicator. Done right it's only slightly less thorough than washing. Once I did a crappy job (before I used the CCD) and had to change applicators pronto and do it again.
I know there's some risk of dirt, but one thing I hated about washing then applying SG was the tiny pockets of water that like to hide everywhere until your applicator runs them over. This meant an extra-careful, and therefore extra tedious, drying session - which is one of my least favourite activities.
