A mixture of mineral oil and kerosene aids in the healing on virtually any wound on a horse. Just mix 50% mineral oil and 50% kerosene (you can buy it in the paint department at a hardware store). You spray it generously on the wound 2 times per day until the skin closes and heals. It's CHEAP and it kills infection and bacteria.
We had a mare who was caught in the barbed wire and ripped her entire chest open so far it was hanging to her knees. The vet stitched it up and said there will be a huge scar. All we did to take care of it was spray kerosene/mineral oil on it and to this day...3 years later...there is no scar. You wouldn't believe that it had ever happend to her.
This spring, her foal got in the barbed wire (talk about bad luck) and sliced up the side of her neck very deep. The only thing we did was spray it twice per day and it healed up perfectly.
We also just bought a mare that had a hard growth on her back leg from a barbed wire accident from years ago (it looks kind of like a branch growing out of her leg). The previous owner clips it off with the nippers and it just grows back. The vet didn't know what else to do to get rid of it. When we got her, we nipped it off and then sprayed the mixture on it and it hasn't grown back since.
This stuff is AWESOME.
My husband's family has been using this mixture for generations, and this is ALL we use for anything that happens to the horses. The kerosene kills bacteria and prevents proud flesh, while the mineral oil keeps the skin soft and supple to avoid cracking and drying. The kerosene keeps the flies off of the wound. The only drawback to this mixture is that wherever the spray hits, it kills the hair along with the bacteria. The hair will grow back just fine, but until it's healed up, the hair will be gone. This actually helps by keeping the hair off of the wound for easy inspection and keeps the hair from matting to the wound.
We just pour the mixture in a spray bottle and keep it on hand so it's always ready to go.