This is from the Buck website.
HOW TO CLEAN AND CARE FOR YOUR SHARPENING STONE
Use a little extra fluid to clean and dry the sharpener after every use. Store carefully. Glossy grey streaks are a good indicator of debris build-up. Clean the sharpener thoroughly.
If using water or water-based honing oil, clean with soapy water.
If using petroleum-based honing oil, use the same oil or kerosene.
To scrub clean, use your finger or an old toothbrush.
Do not drop your sharpener. Being made of stone, it may break or chip.