I have heard that
Molkosan have helped many dogs with yeast problems. You can mix it in the dogs food and/or rinse the dogs ears and skin with Molkosan dilution.
Manda (5 years old) didn't have any problems with her ears until this fall. Then three days after a changed her kibble to an another Manda started to whine while shaking her head. I took her to a vet and she had a bad bacteria infection in her right ear and an yeast infection in her left ear. Manda got some antibiotics and painkillers, and her ears were cleaned every second day with
Otoclean.
The antibiotics helped to get rid of the infections but the main reason for the yeast growth and infection was in the dogs diet, so I changed her diet immediately. I have been feeding my newfs RAW/BARF before and now I changed them back to RAW. Mandas diet is now based raw meat, meaty bones, tripe, oils, eggs and butter milk. I'm not giving them veggie mush at all at the moment, but something green should be added in their diets (carrots, apples and other sweet stuff should be avoided, because sugar "feeds" yeast). I give Manda some probiotics (even if there are some probiotics in the butter milk) and garlic every day. Brewers yeast is not an option as a vitamin-B supplement for dogs with yeast problems (if you are giving your dog kibble check that there are no brewers yeast in it). Manda don't get grains in any form, that includes also her treats.
Mandas diet has worked well for her and her ears look and smell great.
Good luck with your newf, I hope you'll find the way to cure him.