Be careful, very careful, when using a farriers rasp. They are very sharp and the rough side has large curved teeth that will cut you to the bone before you know it.
Old, used ones work best on wood as the new ones are so sharp they can be too aggressive.
The first time one of those big sharp teeth grab and tear off a chunk of your purty curly maple you'll wonder why you ever thought it was a good idea.
Personally, after trying them on gunstocks I find I don't have the control I like. I now only use them on what they are made for; Horses hooves.