As I've gotten older, my feet have expanded and I seem to have started to have a propensity for heel blisters. It's happened with numbers of shoes, from Sorels while snowshoeing, to very well broken in Danners and Keens. Even trail runners on occasion. I've thought about using a liner sock to reduce friction. Good idea? Are silk ones good? Any spray- ons or other solutions? I'm wearing mole skin on one heel right now; 8 miles with the snow platforms gave me a good hot spot yesterday.