The proud flesh is a protective mechanism for horses, its a soft vascular tissue that grows fast to close the wound. I've pealed or cut it off with good success but most would probably more comfortable having a vet do it. There's a powder you can put on it to prevent it but it also slows the healing. I believe its called "wonder dust", be careful what wounds you use this stuff on, many vets say not to use it at all. Mine recommends using it only when absolutely necessary. Its kind of an acid I understand.
Compression can prevent proud flesh pretty well. I cut some off a horse last spring and the vet had me wrap it fairly tight and leave it alone. He said the continuous cleaning people do every day or so is actually harmful, and causes proud flesh because it re-aggravates the wound and activates the proud flesh response.
Good luck with it and let us know how it turns out.