What can be used to clean tools that I have used in the application of your polyurethane sealants?

If the product is still soft, Xylene or MEK can be used to clean the tools but because these are solvents, be very careful. Safety goggles and chemically resistant gloves should be worn. If the product is hard, then mechanical means must be used for removal. This can be a grinder or a chisel and hammer for example.