heat up the grip with a heatgun. hold it on long enough it'll heat all the way through the rubber, but don't hold it close so it melts.
wrap a towel around the shaft of the pole, and put it in the vice loosely. put your foot up on the table and pull. it'll pop right off and you can use a pipe cutter to cut it. when you put the grip back on it'll stay after it cools.
im assumeing you are trying to save some money cause they sell poles in shorter sizes.
if you have access to an air compressor, take like a basketball needle and nossle and stick it under the grip and blow air in. grip will huvor right off. its how i get old bike grips off
Ok get a big arse shifter and adjust it to the size of the shaft, hold higher the shaft up and smack the grip off. I'd draw u a pic but ... u'll figure it out.
Just soak it in hot water, I wouldn't go boiling hot, but pretty hot anyway, for about 5-10 minutes, make sure any screws you need to take are out, and pull...not too complicated.