I've done this many times and the key is a little heat and friction. Luckily, both are achieved by rubbing a plastic knife back and forth over the area and it will work like a champ. Some of the plastic from the knife will actually be left behind on the blank as you do this, but it can easily be wiped off with a fingernail or papertowel soaked in denatured alcohol. It sounds odd, but this really works and the plastic knife will not damage the blank. Try it and let us know how it works out.

HTH,

Lou