All you need is about a tablespoon's worth which you rub for a half minute or so between your hands, just like when you wash vigorously with soap, really. Rinse well with plain water (no soap) and towel dry. Your hands will smell like coffee for a little while, yes, but they will also feel amazingly smooth.
This works best with very fine (espresso) and fine coffee grounds. Be sure to rinse under rings, if you wear them.

