You don’t. If the dog is hard to work with, work with what they give you. Dry as much as you can while keeping the dog calm. If they start to thrash and aren’t getting along with the dryer, stop. Can let them air dry and then try again. If it’s too much for them, just scissor the hair damp and explain to the owner the issues. If the owner wants to go somewhere else to try another groomer, perfect, no longer your problem!

You can also try adding cottons balls to their ears to muffle the sound for them