Hypnosis
For many compulsive skin and finger pickers the act of picking is done in a semi-tranced state. This is different than those whose habit stems from an Obsessive Compulsive Disorder, which usually has a ritualistic component — the obsessive picker stops whatever he is doing to pick his fingers or skin in methodical manner.
If you pick your skin or fingers without really being aware of it — its more a way to “space out”, relax or relieve boredom — then hypnosis is a natural treatment for the habit.
The reason hypnosis can be so successful for the”entranced” finger picker is that self-hypnosis is already happening when the person picks. Working with a qualified psychotherapist, one can easily develop a non-destructive routine to replace the finger picking when you just want to “tune out”.
For finger picking cases beyond just boredom, relaxation etc. — understanding an impulsive cause of the habit it critical to kicking it.