Found this by doing a google search.
Here are some ways to remove Woodland Scenics Flex Paste:
Before it cures:
Acetone or mineral spirits
Use these to remove most residues, clean application tools, or remove Flex Paste that hasn't fully cured.
Sharp tool
Once Flex Paste has fully cured, use a sharp tool like a chisel or putty knife to remove it.
Clean, dry cloth
If Flex Paste gets on your skin, wipe it off immediately with a clean, dry cloth. Do not use water.
Here are some tips for removing Flex Paste:
Before using acetone or any other solvents, test it on a small area of the surface first.
Follow all safety precautions, including avoiding open flames and using protective eyewear.
For metal, use a damp rag and acetone.
For wood, fabric, or carpets, use mineral spirits.
For the body of a vehicle, use a small amount of toluene.