: wouldn't the acetone also attack the epoxy?

The epoxy is resistant to acetone penetration as long as it isn't exposed to the acetone for a long time. The acetone vapourizes very quickly. I have successfully used acetone to wipe down sanded epoxy finishes in between coats. For me, I need to do some pretty major repairs to my kayak so softening the outer layer of epoxy is good. This allows me to sand any rough spots in the epoxy with greater ease than otherwise.

Robert N Pruden