These pictures were taken 29 days apart. The frogs look fairly terrible, but I think in the second picture the deep central cleft is filling in and looking rather less grotty? I have been using an OTC Athlete's Foot spray for two weeks and as everything else has remained the same it is probably safe to assume that the spray has made all the difference.
When I bring the horse in at night, I scrub the foot thoroughly with plain water, dry it with paper towels and then spray. The can says to use twice daily, but once seems to be working okay.