There a couple of good ear mite remedies. Milbemite is the most effective we've used so far, but not all vet hospitals use it...it has the advantage of a very short treatment period.
Tresaderm is also very good, but can be difficult to administer, since it must be kept refrigerated and even the best-tempered cat will object when you pour ice-cold liquid in its ear every day for a week. If you have to do Tresaderm, I highly recommend shoving him head first into the sleeve of an old shirt until his head pops out where your hand would be. Keeps all the pointy bits safely restrained. :-)
Revolution also works, but takes a while to kill them off and you have to do an ear cleaning too to get the itchy crud out.

However....if he only had his run-in yesterday, it's unlikely he picked up ear mites at that time. The eggs are transferred passively from one animal to another and take four days to hatch, followed by a breeding cycle before you see an active infestation. If he has mites, he must have acquired them previously. Other possibilities are an injury to the ear incurred during his battle, or an allergy to something he encountered while on his adventure. Your vet will be able to do an ear swab and see what's going on down there.

And yes...topical ointments on cats are usually a waste of time.