You can also turn the key off 'till it almost dies, then shift.
My favorite new thing is powdered graphite.. the little tubes that you squeeze and spray. Originally used it to lube the clutch bushings, but soon found out it lets the belt slip on the engine clutch shaft when idling. I sprayed mine today while idling in nuetral, and the belt and trans clutch rolled to a stop. Makes the cvt and belt work really smooth. Doesn't last long.. I carry it under the seat.
But if it's idling fast enough that the engine clutch is gripping the belt, thats a too fast of an idle problem.
To Invent, you need a good imagination and a pile of junk. (Thomas Edison)