How do you calm a dog enough to be able to clean its ears?

My dog needs his ears cleaning, and I know how to do it since I did a Dog Grooming module at college, but he is very snappy when it comes to things like that. I need to treat his hot-spots too but he gets snappy again... I need to know how to relax him enough to be able to help him. I have tried muzzles, (and need to replace his fabric one with a basket muzzle,) but even if he has a muzzle on he still wriggles a lot.