I have never sharpened them. They don't need it. Mine have 21 inch handles. They are a little awkward in my small hand at times but I loose too much leverage without it.
Don't skimp on a rasp or knife either. A rasp should shred hoof wall like shaving coconut. I've got a Heller rasp right now. It's only the second one in 20 years. The old one was still better than any diamond rasp I've tried even after using it for 10 years. I keep the old one just in case the Heller doesn't hold up. I also keep it slipped into a piece of pvc pipe so I don't dull it or shave my knuckles. The old one is also draft horse sized. Maybe because I learned with one big like that I like it better. I just didn't feel like wading through the giant selection meaders had when I bought the other.
I do know my hands and forearm are loaded with little scars from knives and rasps skittering off rock hard feet. Enough so I considered wrist protectors meant for archers at one point. Mostly doing the draft feet because I wasn't big enough to hang on and put some muscle into stuff well at times.