1. Wipe as much of the dry debris from the holes as you can with a scrubber sponge.
2. Still not spraying straight? Mix a solution of equal parts white vinegar and water (you'll need about 1 cup), and pour it into a plastic bag.
3. Put the plastic bag around the showerhead so the holes are immersed in the liquid, and secure the bag to the shaft with a twist tie.
4. Allow it to soak at least 15 to 20 minutes (up to an hour if you can).
5. Remove the bag and wipe away loosened deposits. Run the shower on hot to flush and you're all set.