I carried a foot file for the entire Pacific Crest Trail(PCT). Foot files are not all created equal. The ones you get in the bath stores are much better then then ones you get at a drug store. They are paddles with what looks to be sandpaper on them. The problem I had with mine, was that its wide paddle made it hard to target the calluses I most wanted to lose– the one on the ball of my foot and the one between my toes from wearing Chacos with the toe strap.
I found a better one then the one I carried. Better because of it’s narrow shape and courser file. It called the Flowery Swedish Clover Fot Fil * #530
Another file I used, to get rid of the remnants of my hike, is one made by a company that makes wood rasps and vegetable peelers. It is a sharp metal rasp. It works amazingly well but you need to exercise a little restraint or you may take off too much skin. It’s called the Microplane Foot File.
I used a hacksaw to remove the handle off the one I carried on the PCT. It weighed .5 ounce (14 grams) after I removed the handle. The Flowery Swedish file weighs 2.20 ounces(62 grams) with handle and the Microplane foot file weighs 2.10 ounces(56 grams) with handle. I would guess half the weight is the handle.
A pumice stone is not in the same league as a foot file. A foot file sands away callouses on dry feet in one sitting and there is no need to soak them first.