I use the dots and the "Gripper", wish I had thought about the shower thing before spending $20 on the Gripper. Oh well, I also use the sand paper dots and at first only used three on my 24" ruler, it was not enough I still had slippage and then added more dots, no more slippage.
In the past, I was rotary cutting challenged, now I cut MUCH more accurately.
JulieM