Every now and then I will use my leaf blower to blow dry the bulk of water off before hitting it with the synthetic chamois. I have found that it's easy to safely blow out most of the water from the mirrors this way.
I have also taken the chamois and folded up a flat corner section that I can insert under and around the mirrors to soak up the bulk of the water that's caught in there. This works pretty well. Also works for the drips that happen around the fuel tank door.
PS: Granted, this is for home washes. I would feel pretty dorky bringing my leaf blower to the touchless carwash...
