bike shops use compressed air but lacking that I use a tiny insulin needle and inject a little soapy water in a couple places-twists right off. good luck at the drug store
I used compressed air - I have an air gun with a long slender nozzle. I also will use a light silicone aerosol lube with a squirter tube when they are really stuck - BUT if you use any lube warning WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING YOU WILL NEED TO CLEAN IT OFF BEFORE REASSEMBLY.
All I use compress air or Rubbing Alcohol. Just use a screwdriver and pour a little between the grip and bars then spin the grip off. Rubbing alocohol evaporates and doesn't leave a residue. When reistalling, pour a little in the grip and slip in back on. If your in a rush spin the grip until it sticks and your're off to the races!
Spray some WD-40 between the grip and the handlebar and it will come right off. To reinstall wipe everything off and used hairspray to slide it back in place and to hold it there.
I slip a ziptie between the bar and the grip and spray 610 silicone spray lubricant in. I hear the bike shops use hairspray it lubes it at first but then becomes sticky when it dries never tried it though.
Spray some WD-40 between the grip and the handlebar and it will come right off. To reinstall wipe everything off and used hairspray to slide it back in place and to hold it there.
I was going to put a centrifugal clutch on my handle bar and I had the same issue. Thanks much to the people who were able to suggest solutions. WD-40 worked for me.