Removed a pair of 30 year old clear Winner's Circle grips yesterday off an old Mongoose yesterday... Used my regular method:
I also use a super thin screwdriver. I very gently and carefully insert the screwdriver between the grip and bar about 1 1/2 inches...
Only difference, I just spray some warm water into the gap. Remove the screwdriver and twist a little. Repeated the process with the screwdriver in a bit deeper.. Take it out, twist a bit more...
Done.
No damage at all to bars or grips. No cost, no chemicals or other crap either.