I've done it both way with CSM. When I tore it I was repairing something, like my 170 had been beached so many times that the keel was worn through in one spot but the previous owner had painted it over and I didn't see the damage. When I did find it (because the boat almost sunk), I tore the 1.5oz csm and tucked it in and around the gouge that was now present because I ground it deep. After a few layers I could start adding cut pieces of 3oz csm and went back and forth between torn and cut until it was filled.
Oh, and use your air compressor to blow out the motor on your fan often. I borrowed a fan from my buddy and after a while the motor was getting hot and started to not turn on. I blew it out and all kinds of stuff (he never blew it out since he bought it) came out. I did this from several different angles until it was clean and it started back up and spun much freer that when I received it.

Sage advice umecheme.  30 years ago when I did my last boat rebuild (stringers and deck on what we think was an 18 almond that looked like a wellcraft v-step), we would patch holes by tearing pieces of mat instead of cutting.  I did both here. Is one way better than the other or is it personal preference?  Thanks for everyone's input. Very cool.

Welcome aboard Mfarmer1020. 

Thanks Rick!

Thank you Rickk. I get it now. I can be a little dense.