Apply Lithofin WAX-OFF undiluted and allow it to work for 5-10 minutes. Add some water, brush, and then remove the product. Rinse thoroughly with clear water. You may have to repeat this procedure.
In case of stubborn, deep-seated stains apply Lithofin OIL-EX in a 2 mm thick layer to the dry surface and cover it with some foil. Remove the foil after about 12 hours and brush off the white powder after one more hour.