Anyway. I knew that lotion could help this problem, but only up to a point (also: requires diligence). About a year ago, I bought some pumice stones, but they are pathetic. I was not prepared to go the sandpaper route without at least trying other products (also, emery boards were clearly too wimpy and I didn't really want to think about the grade of paper I was going to need). Amazon's reviews seemed to think this was worth a try.
Wow. Is it ever. Do _not_ touch the screen with your fingers -- they'll catch at a minimum and if you are a Delicate, Fragile Flower, they might do some damage. The handle means you can safely go after a heel callus, however; when the screen fills, you really can just tap the ewww off and continue (however I have noticed it is dulling, so I've ordered replacement screens). You're supposed to use it on dry feet, which is convenient -- no prep involved, really (altho I suppose if your feet were really dirty that might be an issue).
The flaky-cracky-mess has been reduced to a nicely shaped, useful pad, which is what Nature Intended, and I even managed not to overshoot (which seems to happen on those incredibly rare occasions when I submit to a pedicure) and leave too little to walk on unshod. If something weird happens and the handle breaks or the replacement screens don't fit, I'll post an update; otherwise, consider this an unqualified recommend for those with persistently, overly thick skin around the heels and elsewhere.
ETA: Read the warning label; if you have limited feeling in your feet, you could hurt yourself.