Here's another piece of advice... if your OLFA mat looks like it has fibers stuck in it, take an art gum eraser (sold at any art/craft store) and "erase" your mat. you'll be amazed at all the stuff the eraser pulls out!
I don have no fancy art gum, but i tired your comment with some good ol american wrigleys boughten from the Walmart, and I sure enough did get a lot o grit adn debris out of my matt.
