I'm not the best tech, but if you have an air compressor, find a small nozzle, slide it under the inside grip and blow away.
Use BrakeKleen or equivalent, put nozzle under inside interior side, blast away.
Then pull like hell
All I would add is that the throttle tube that the right grip is attached to is plastic so some caution/ care if using an X-acto knife or source of heat. Slit them longitudinally with the knife (carefully) and peel them like a banana
I have an old 7" long, thin (maybe1/8th in shaft??) slotted head screwdriver that I simply insert between the throttle tube and the rubber grip, then roll it around the throttle tube - the grip will pull right off. Works on the non throttle side too.
And, I never glue new grips on. Usually nothing required to hold the grips in place, but if they are a bit loose, then a wrap of electrical tape around the bar will prevent them from moving.