Our metro had yucky ears, but loved to have them rubbed...to clean them we would wrap a paper towel around our ears and rub them...he would lean in to control how deep our fingers went, but that's how we cleaned them. He was never aggressive toward the vet...but are they exhibiting fear? I've had just about every vet we saw act afraid of our shepherd! One vet even had us hold his head before he listened to his heart!
I get the fear---really I do! But they went into a field where instead of someone cussing them out, there are growls and snaps. I work with some patients that can be paranoid schizophrenic...and THOSE are some scary patients, especially when they have a foot and a good 100 lbs on you! That's freaky...but I don't charge in there with a sedative just to do an assessment! What are you feeding him? Perhaps a week or so on a RAW diet will help clear out some of the problem along with the cleaning advice you've been given? If you wanna do the sedative yourself, I would still listen to the vet on how to do it. As an RN myself who can stick a vein in the most combative patient I would never assume that I can do the same to a dog. Knowing how to given an injection/insert an IV in a human is not the same as an animal.