It is probably just a gunk buildup which if so, will not hurt him in the least. It is cosmetic more than harmful. If by chance it is fungus, then it should be checked out. I've had some rescues/rehomes come in with ears that I swore had to be fungus and a week later with some rubs, the ratty edges and fingers came right off.
Some of them get a gunk build up very quickly and others never do. My Peaches who was an absolute neat freak had to have her ears cleaned on a weekly basis or she had gunk building up. Don't know where the dirt ever came from cause it certainly was never on her. lol
If he won't let you rub vasaline in, try just giving the ear a swipe every day. It will take quite a while but the gunk still should loosen. You can also try wearing a glove on the hand you use to touch his ears. Sometimes with some protection from quills you can wiggle a finger into the ear area.
Personally, unless I really thought it was fungus, I wouldn't gas one just to have their ears cleaned. There is always a risk from gassing.
Good luck
