It can be done with a regular blade like Bob_Golf said, you have slit the grip just a little bit then tear it off, when the grip doesnt want to tear right just nick it again with the blade.

When I installed my grips last week, I used a mix of the air and the tape/solvent method. I would put the tape down then fill the grip with solvent and pour that over the shaft/tape. Then I would install the grip a 1/2"(to the tape), and use an air gun to push it past the tape. Just try and have the grip aligned close because it sets fast. This ways is lot faster and was only taking me a minute a grip.