Chesney used to have really soft feet. I did some reading on a sled dog forum and started supplementing him with zinc. It's just the zinc you get from a health food store or pharmacy. I started off by giving him a pill every night with his dinner for a week or so, then cut back to 3-4 times a week then down to 2-3. Now I give him a pill when I remember (usually once of twice a week). Now if he gets a little gimpy after running on ground that used to make his feet bleed, I see no signs of torn pads or very minor blisters (start of torn pads) that heal much faster then they used to.
I wanted to add that I give it to him with or after his dinner since zinc can upset the stomach (at least it upsets my stomach) when it's empty.