other then muzzle at the vet, I cannot comment on that. However, I can suggest a few things that will help your dogs ears and will not cause pain and suffering, will kill the microbes and emulsify the gunk so you can get it out.
1) Coconut oil (raw organic), put some in a sep. glass container, wrap your finger with thin soft cloth and dig out some C.O., will melt on contact with the ear as you swirl around cleaning it - the oil will melt into ear canal and emulsify the deep down stuff (yeast), rub the ear at base of head to help work it in. As stuff moves up, CO again for cleaning - this will not hurt, KILL yeast and bad bacteria and will sooth inflammation.
2) Ear oil, St francis or NOW or other - Olive oil base with Mullein (excellent antibacterial/anti-yeast herb - soothing), garlic, St. Johns wort, tea tree and calendula (also very soothing and healing)
3) zymox - available online is for ear infections and has a probiotic in it to repopulate the good bacteria that keeps the bad and yeasts at bay. Also have a mild cortisone version for tuff infections that require.
You can buy a tincture of Mullein and add to the CO (just 4-5 drops/ tblsp of CO) and create your own ear oil. My dog wouldn't tolerate any ear probing with any product until I started using the coconut oil, everything else, the gunk just kept coming, after first treatment with CO, noticeably better, I think needed to do 3-4 x and then touch up month or so or whenever saw signs of yeast.
The vet is right, no abx. is going to treat a yeasty ear.
Hope this helps
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion. - Unknown