If you are ready to use them now you can shread them while still "green". I would cut down the sheath that holds them together and soak them in warm water while pulling the bundle of fibers apart.
If you dry them first you pound them until the fibers part then seperate with your hands. Using a rawhide or wooden mallet on a hardwood base will help protect the fibers but some folks use a ballpeen or other hammer on an anvil.