To clean the fabric whiskers from my rotary cutting mat i dry scrub it with a greenie which is really designed for scrubbing dishes.
Cutting mat has grooves.
I have one old mat soaking now.
It reminds me of a c filter material there is a trick to removing all of the fabric particles from the cuts in the mat.
The other posts about using a sharp blade are true as well a dull blade cuts a wider groove allowing the fabric to be pushed into the mat.
I would think if you have to push so hard that you leave grooves in your mat you either need to replace your blades more often or definitly switch mats my 24 x36 mat took almost 10 years before it was faded kind of needing to be changed out you really should not have to apply much pressure when cutting with a rotory cutter and you should never use a knife or other tool on a cutting mat they are made for rotory cutters anything else will damage the mat once there is signs of damage it.
If you have a self healing cutting mat it needs to be re hydrated to stay self healing.
Cut the artwork opening in the normal fashion with the mat face in.
I just gently bend the cutting mat over the edge of the table or over a coffee can.
The idea of using the back of the mat for cutting batting and fleece is a good idea too.
A v grove provides an accent line around the outside of a mat opening giving an effect similar to the ruled lines on a french mat.
It might not seem like a big deal at first but over time all these grooves add up and can affect your cutting accuracy or worse snag your fabric.
Remove the mat and place it back in the machine face out.
When the moisture is gone the mat dries out and will have cut marks and dull your blade.
Soak the mat in room temp water for about and hour let dry.
When you use a rotary blade on a hard plastic cutting mat you leave a small groove in.