If you only foam and rinse (and skip the mitt-washing), I believe you run the risk of swirling and scratching the surface upon towel-drying. If you must foam and rinse (and don't have time to actually wash with a mitt), you may want to consider simply blow-drying (no towel), then cleaning your windows and mirrors. I suggest cleaning the windows and mirrors because they are most susceptible to showing water spots.
All that said, I've tried this method in the past, and I've realized that if I'm going to do a good (thorough) job of blowing the car dry with zero towel usage, it takes a LONG time, thereby negating any intended time-savings of skipping the mitt-wash (two-bucket method wash). Furthermore, you'll likely be left with some residual dust on the vehicle's surface.
If your okay just hitting it quickly with the blower and leaving a substantial amount of water on the vehicle, then I suppose this method could save you some time (but still won't compare to the cleanliness offered by the mitt and the two-bucket method on top of the foam gun/cannon).