Warm water that has been soap-treated is an effective hardener. When working with resins, denatured alcohol, isopropyl alcohol, or acetone are all effective solvents.
First, it is best to use some rags to remove as much of the material as possible by soaking it up and/or scraping it off, and then you should clean the damaged areas using one of the solutions given above.
Solvents will no longer be effective in removing cured material. It has to be sanded down.