We cut lots of pellon, insulbrite, and other stuff that gets stuck in our big mats. We try to cut those orders last of the day, then we clean our mat with a special little rubber device that you just rub across it.
We also sell those, they work really well and one will last indefinitely.
http://www.quilt-kits-online.com/pro...php?prod=6719A
If you get one of these someplace, read the directions. After the cleaner cleans it off your mat, you run the rubber thing under cold water and scrape the collected gook off with a fingernail.