Sorry if I missed this in the posts, but I searched and didn't find it.

There's a product out now, quite inexpensive and available in most drug stores and big-box retailers in the US, called "Ped Egg." (I think I spelled it right.)

It kind of looks like an egg, and you rub it over the skin on your soles and it painlessly shaves off the dead skin and callouses. Haven't needed to try it yet, but if I couldn't deal with my minor callouses with an emery board, I'd go for this product in a heartbeat.