You can try removing the varnish using mineral spirits (a.k.a. "paint thinner), since that's the thinner in the varnish, but I suspect that you'll need something more aggressive such as lacquer thinner. Ultimately, you may have to resort to paint stripper, as has been suggested already.

As has been mentioned, acetone isn't very useful, as it's too volatile. More importantly, it can damage the epoxy, which you obviously don't want to do.

If both problems have occurred with the same can of varnish, I'd toss it and get some fresh product.