quick detail and a MF towell is the quickest way to touch up.
if it's dirty to the point where it's too much to spray/wipe off, you gotta wash it.
How clean a car is is totally dependant on how much time the owner puts into keeping it clean.
it's just the way it is.
I do use a CF Duster occassionally, and only if the car is dusted. lightly wipe off the dust, then spray/wipe.
if I'm at home I use compressed air instead.
if you push hard or have heavy, rained on or dirt there, wiping it with the duster will scratch the finish like Handz so elequently stated.
Side note - I do have a california dash duster and that is handy for touching up a dusty dash...
if you or a detailer were to polish out the car and put down a good sealer and wax. it would be easier to clean and quicker to wipe down, water beads up and dirt doesn't stick as well.