These are the two drying agents our vet has given to us over the last two years.
#1) Vet Solutions Swimmer's Ear Astringent manufactured by Vetoquinol. Website is vetoquinolusa.com It is a gel, which is a bit easier to control, but it sounds like a ketchup bottle.
#2) Virbac Epi-Otic It's sold as an ear cleanser but it is listed as cleansing, drying, and non irritating. Our vet suggested this one just recently. It's a very thin liquid.