Ah, the torment. Both my sons suffered like crazy from Athlete's feet. The Foxfire books do recommend putting your feet into fresh cow poop - and leaving them there for a long period of time. For my sons, however, we used someone a little less odorific. They first soaked their feet in a solution that penetrates and softens. Then they applied tea tree oil, T36-C5, applied to the affected area and rubbed in. Do this every evening until there are no remaining symptoms. Much less expensive than the sprays, creams, and medicated powders we tried and much more effective.
Happy feet!