I haven't used this on a dog's ear - but a donkey's - it works
from Jim's book (treating people)
"Bentonite Procedure
Purchase the clay and mix it with 50% Vaseline (petroleum jelly).
Then smear this liberally on the affected area. If this is your feet and
toes, put socks on over the mess and go ahead and go to work. If
this is anywhere else on the body, spread the affected area liberally,
cover it all with a clean cloth, and tape the cloth down. You will need
to put a fresh mixture on at least once every 8 hours. Regardless of
where the infection is, it will be gone in about 3 days after you begin
this regimen."
For "hot spots" on our neighbour's dog (shave the hair) then wash the area, then spray with a solution of MMS (10 drops / 30 ml distilled water) leave for a while (scientific eh?) then smear with the Bentonite clay mixture