Get a blow dryer and make sure its blowing out hot air. Blow dry a somewhat small section (4-6inches) for roughly 2 minutes and the grip tape will start lifting up. Continue to do so around the sides and move up to the nose and the opposite side. Eventually you can lift the grip tape then just cut off a section you want.
Look up how yo replace grip tape on YouTube. rat vision has the best video IMO.
Personal note: Stacking grip tape has never really worked well for me, that's just in my experience!