I don't know about your dogs, but I know mine absolutely hates the sound of a hairdryer.
Even if I'm doing my own hair and haven't made a single attempt to point the hot air at him, he still gets spooked and hides from the loud, jarring noise that comes from my post-shower gadget.
So, when it actually does come time for him to be dried off, I have to stick to the simple towel method that doesn't really get him fully dried and leaves my laundry smelling like wet dog.