Not all shoe textures look good on the barefoot mesh. This is due to the bad mapping for the toes.
Shoeswap tutorial:
http://digitalperversion.net/gardenofshadows/index.php?topic=18661.0With pictures, and every step is explained, so it's quite easy (even if the tutorial looks long).
* GoS might be a little slow in loading, or seemingly not load at all. This is due to their recent problems. Just try again if it doesn't load.