I'm surprised that nobody has mentioned THORNITS powder which works wonders!! Up until a friend recommended using it about six years ago (a large pinch once a week) I was forever at the vets with my Bassets' ears needing antibiotics, cleaning etc and I think liquid cleaner keeps the ears moist and encourages bacteria.
My two Bassets will be four years old towards the end of this month and neither has ever been to the vet for ear problems because once a week they both get a big pinch of the powder in each ear (rubbed in) and it keeps them clean and sweet smelling.
If dogs ears do get a bit dirty, or itchy, just put the Thornits in every day for a few days and any problem will clear up. I have recommended it to other friends and all have found it to be brilliant and save a lot of money at the vets!!!
You probably can't beat the old-fashioned remedies and Thornits goes back to 1907.
http://www.petmeds.co.uk/p-528-thornit-ear-powder.aspx (click on reviews)
I'm another fan of Thornit powder, have been using it for years & fingers crossed that neither have had ear problems.
Would also add that ears, like glands often go with skin problems. Have tried & fought for years to get one of ours skin under control & at long last though I don't like steriods, he has been on a months course of AB's & is on a reducing amount of steroids. He has not itched for 3 weeks, his skin is great & his ears that have always been filthy (having to clean every day) are transformed. I'm hoping that we will be able to get him down to one tablet every 3rd day. Good luck