I bought a cutting mat cleaner. It says it's a natural product. It looks like it's a soft plastic to me. It bends and it's about 5" long and 2" wide and angled at each end and you brush the cleaner across the cutting mat. Imbedded fibers are being pulled out of the crevassas as you brush it across. I clean it under cold water afterwards (the cleaner). You can find it here:
www.designstoshare.com. I bought it at my local quilt shop a couple of years ago and it seems to work really well. I really really really like it. I paid $6.00 for it. Probably can find it for less if you go directly to the company or to an online store.