You will not be pleased with the results if you try to use that as a sanding tool on plastics. It will eat through the plastic and probably melt some of it. Way to many RPM's.
I use one of the cheap $10 electric rotary tools combined with a dimmer switch to get the RPM's down.
I do not know if using a dimmer switch with your rotary tool will damage it.
I also use a "Sonic Scrubber". Its basicly an electric tooth brush on steroids. I use velcro to attach sanding pads to the head of the scrubber.