Corn meal is better than oatmeal for grabbing the oily residue off of the rubber.

Typical office supply bands... yo can re-use ONCE. and then only if the second use is within a week of the first. You never do get all the oil off of them and they break down.

The Gum Rubber... you can reuse a couple of times... but compare one that was reused to a new one some time. You'll quit reusing them.