I think it depends on the dog. Our basset needed her ears cleaned at least once a week or they'd get infected. My lab needed hers done every time she went swimming to prevent infection, but not as often otherwise. My current dog, I clean them maybe once every few months? I know others of her breed that need regular cleanings, but hers seem fine without much. I always use ear cleaner after a bath as it helps dry any water that might have gotten in there, and its just a good routine to make sure it gets done. What sort of dog is he? i'd probably clear up the infection and then sort of wait and see, I mean, examine the ears regularly, but if they seem ok, your probably good.
As far as ear drops, I'd offer lots of treats. Really high value treats. Something he'd do ANYTHING for, not like biscuits, but like cheese or chicken bits. Offer them both for the drops, and then sometimes just play with his ears and treat, no drops. I'd start out doing ALOT of handling of his ears and treating without the drops, so more times than not, there's nothing unpleasant. I'd guess you need to give them once or twice a day? So make an effort to handle his ears without the drops and lots of treats maybe 4 or 5 times the first few days, so 5 times will be no drops, and only once or twice will be drops.