I find tying them up in an old t-shirt and running them through the washing machine cycle usually does the trick. However, for that really tough grime that gets lodged down in the bottom of the cane in the hat&cane or the crevices in a small key mold, there's really nothing like a good stiff wire brush and some elbow grease.

A little vaseline to bring out the colors when you're done, and Viola!