Years ago someone fanatical (like most of us, or why would we be on a detailing forum) showed me this method, which I have used ever since....
Go to Home Depot and buy an Ostrich Feather Duster. Yes, that's right. The Ostrich Feathers are super soft, and that is how I dust off the car (not dirt, mind you, just atmospheric dust, or after a drive on a nice day). It is very effective and doesn't harm the paint. THEN, use the detail spray.
You may get some strange looks when you're using a feather duster on your car, but it's a VERY effective method.