hairspray. good for on and off.
i would suggest a bamboo skewer in place of a screwdriver, they are much less likely to scratch or gouge your handlebar.
or if you have it, and air compressor is even better. fill the handle bar with air and the grip simply slides off (cover any holes with your opposing hand)
try putting them back on dry when it comes time to replace. otherwise, light spray of hairspray does the trick