Kutzall tools require little maintenance, but if you happen to get gooey material "loaded" in the teeth, easily clean the tool with one of these methods:
Burning (for wood): The heat won't harm the wood! Pass the flame from a propane of butane torch over the clogged-up area. Now remove the charred residue with a fine wire brush. Inspect for damaged teeth, and carve on!
Soaking (for wood, plastic, soft stone, etc.): Immerse the tool in a can or jar of solvent (don't immerse Hand Rasp handles). When the material has softened, brush out with fine wire brush. Dry off the solvent, inspect for damaged teeth, and carve on!