a window fan with a filter helps cut down on the dust. Dirt nibs are to be expected when painting in yer garage though. if you or someone you know has a high speed buffer you can still make it look like glass as long as you put on enough clear. runs can be carefully shaved down with a single edge razorblade ( tape the corners ) , then wetsanded a little bit with 1500 grit (use a block on runs and other large imperfections). dirt nibs will sand out with 2000 grit. orange peel should be blocked down with 2000 grit. finish everything with 3000 grit and you'll barely have to buff it to a beautiful shine. remember to keep your paper very clean as well as the paint surface, continuously spraying both with water. Dry the paint surface often to make sure you are sanding out the larger grit scratched rather than gouging debris into the fresh paint, making it look worse. white looks good buffed out with just rubbing compound, black takes 3 consistencies of compound to look good in the sun with no streaks.
In body shops, with high dollar downdraft paint booths, they still get dirt nibs in the paint.
