When my vet suspected Kia of Mange, she gave her a series of two shots of Ivermectin. My vet does not do dips because they can be very toxic. The shot is much safer.

I didn't pay $100 for the shot. I paid roughly 20 dollars per shot. After two injections a week apart, Kia was still itching and it was determined she had allergies.

Sarcoptic Mange is VERY contagious and I don't think your obedience instructor will want your dog around others until he's all better.