If the dog has long hair, trim it from around the spot/s. UV light is very good anti-fungal treatment.
Any of the anti-fungals (lotrimin, lamisil women's feminine products etc.) will work. But they take time to thoroughly clear up.
I used to get it a few times a year. Cleaning regularly and treating it with something also to dry it out is helpful. On a small spot, I would use clorox. Betadine or alcohol can accomplish the same thing, to dry out the sore and tissue. Makes it hard for the fungus to survive and grow.
