I'm not really sure what causes this but my min pin has crustiness on the tips of his ears. I can't tell if it's earwax or dry skin or what. I've tried scrubbing it off and it bothers him because it's a bit waxy but takes the tiny hairs off the tips of his ears as well. So far the only solution I've found is to mix ear cleaner and vaseline and leave that on for an hour then wipe some of it off.
I ran into a large manchester terrier in the interior that had the same kind of problem but his was so severe the tips of his ears would actually split and bleed.