In reply to rlocock:
I've done this with a couple of pairs of approach shoes that I'd worn the heels down on by wearing them around town as my day-to-day shoes (yes, I know!)
My most successful method was using Shoe Goo to do the main rebuilding (taping around the edges to hold it in where the wear went to the outside of the heel) and then switching to Freesole for the outermost layer or two: it's less slippy than Shoe Goo, if less tough. I also added in some rubber from a 5.10 Stealth Paint kit, but that was because I still wanted them as fairly grippy approach shoes. They worked well and lasted for at least a year or so!