I've found that if I put a bandage over a blister and strap it down tight, the blister will shrink down and reattach. It's not attached very firmly, but if you protect it for a few days the skin under it will have had a change to grow out by the time the blister detaches and tears off.

EDIT: I'll have to try that spenco stuff. It looks like it might be a more efficient way of doing what I'm already doing.