Set up a hide with some damp (not soaked or dripping wet) moss and put it in the enclosure. The best time is when you see your snake is in shed or after a bad shed. It helps loosen up the old skin. You don't want it to be too wet or it can get moldy (cause illness)!!!! I find it better than soaking a snake because the snakes don't generally stay under water for very long but will stay in the moss hide for long periods helping loosen retained sheds or eyecaps or preparing a snake for a quality shed!

Just dont leave it wet for long periods(more than three days) it should dry out after a couple of days. Then re-wet if needed.