You can check for a yeast infection by smelling his ear- it will smell like dirty socks.
I haven't yet had to treat a rabbit with an ear infection, but I have treated dogs and cats for infection and/or mites, and I'm sure the same procedure will work on a rabbit.
You can make your own ear wash at home. Mix a solution of 1/2 cup water, 1 cup white vinegar and 1/2 tablespoon of Rubbing Alcohol. Some people recommend distilled water, which is probably best since the minerals have been removed- but plain water is fine too.
The vinegar changes the ph of the ear which inhibits growth of yeast and bacteria. The alcohol helps to dissolve wax and has an evaporative effect. I like to pour some solution into a small squirt bottle or syringe (needle removed, of course) so I can warm the solution prior to using it- it is more comfortable for the animal and helps soften the wax if there is any.
Fill the ear canal with the solution, squeeze the base of the ear shut, and agitate it back and forth- you'll hear a sloshing sound. This will help loosen debris. If buns are like dogs, when you let go he will immediately shake his head, flinging fluid everywhere... so you might want to do this outside.
Dogs and rabbits have an "L" shaped ear canal so you can gently clean their ears with a cotton swab to remove wax and not worry about puncturing the ear drum. Always moisten the swab prior to cleaning the ear so it is less abrasive.
Since there is some redness at the base of his ear, you might want to just flush his ear once daily or every other day for a couple of days and hope that does the trick, since his inner ear canal may also be inflamed and thus more likely to bleed.
