I've heard good things about Fiske's but have not used it yet :?
Hoof and hide balm or the Skin and Wound Salve. http://www.fiskes.ca/index.html and https://secure.syrvetcanada.ca/img/product/description/FISKE'S_PRINTED%20PRESENTATION%20BOOK%20rev%20JUNE%208%202011%20retail.pdf
I've cleaned the crusty off regularly, then kept it soft with the Vet's 'green cream' or furican (sp)-the yellow balm. It usually clears itself up when our dry season comes around.
The hoof. Slip a plastic bag over the hoof and up the leg. Tape the bottom in place. Pour a can of sauerkraut into the bag. Tape the top shut. Wrap the entire thing in vet wrap. Leave alone for 3 days.
Most importantly is to figure out what caused it. Eliminate the source so it won't come back.