i have something that is called a "MAT SMOOTHER"
i purchased it from Clotildes- i think for about $15
it is like a fine sanding disk - round- with a handle- it works wonders (i've been using it for 7 or 8 years now) to clean up & smooth my mats- keeps them like new- it was a great investment....smooths out any rough patches along with keeping my mat clean- i thought i had ruined my mat cutting silks one time- the smoother fixed it all!