I got my G2 Throttle Tamer installed. My air compressor is a 2 gal 100 psi unit and it was not up to the task of loosening the grips.
I wound up using a small flat blade screw driver to loosen the grip from the throttle tube (TT), and then used a longer phillips head that was about as long as was the grip. I rotated the screwdriver around the circumference of the TT under the grip, and then it twisted off pretty easily. That was the hardest part of the job. I did not damage the heated grip using this method.
I used a 25% alcohol/water mixture to lubricate the grip to slide over the new TT (the same liquid I used when installing the bag protector plastic sheets).
One cautionary note. Take a pic of the grip setup before you start removing anything and one showing the location of the warmer wiring exiting the grip. These will help you remember how things were positioned and how to position the grip, etc when you are reassembling the grip and wiring covers.