I use Corona's Lanolin Rich Ointment myself.
My QH mare has a scar on her rump. So far, nothings ever grown back on it. I had to slather my other guys in ointment anyways, so I put some on her rump just for the heck of it.
I go out today and was looking at her scar...she has hair starting to grow on it again
. Just a little, not a lot, I put it on about a week ago and haven't since then. Up until now, the area has been barren, no hair growth what-so-ever. After I put it on, I remember a day or two later it was fresh looking again, instead of black and flaky like it usually is.
I'm testing it out on my two other geldings as well. One got some nasty scratches on his chest and the other really took off a swath of skin on both his back legs. Completely forgot to look at them this morning like an utter dork, but I'll be going out again either later today or tomorrow so it's not a huge deal.
Divo got a nasty cut and several scratches on his chest, went through something when Loki chased him. Now, unless you get REALLY REALLY close, you can't tell that anything ever happened. Save two tiny ones that are just finishing up with healing. The only way you can tell that anything went on there is because the new hair is still shorter than the regular hair ;)
Used it a lot on Sam, since he was the lowest in the pecking order he got bit a lot, and in the spring would rub the hair off his forehead. Always grew back with Corona's
Love that stuff to bits. I keep a jar in the house just for the dogs if they get irritation or scratches.