Narrow bladed screwdriver under grip edge, slide in straw off can of WD40/GT85. Squirt a little in. Pretty quickly gives slack under grip, either work it round or push straw in further and/or add another squirt. Keep going and they soon slide easily off.
I wouldn't (personally) cut off as it'd probably score the underlying metal with the blade tip. Not saying this is significant but I'd rather avoid doing so.
Discard new packet of regular grips and go spend some more money on lockons, just a whole world easier and quicker. IMO life is just too short to fanny around with "old style" grips / hairspray / spray paint etc 😉