I just completed this switch. I love my LG poles, but after about 2000 miles the grips started turning my hands black. To remove the old grips, I carefully cut them lengthwise, without pushing so hard as to score the carbon pole. I used pliers to twist off the top plug. If you don’t want straps, leave the plug off. I got a piece of 1/2″ pvc pipe and beveled one end. It has an outside diameter very close to the diameter of the pole. Heat one of the new grips on a hot pad in the oven for 5 minutes at 250 deg. Pull it out of the oven and slide the pvc pipe in with a little twisting. Leave the pipe in until the grip cools. Carefully slide the pvc pipe out. I put hair spray on the pole and it slipped easily into the grip. When dry, the hair spray helps hold the grip on, similar to the Windex suggestion above. Repeat for the other pole.
I wanted straps, so the job was a little more involved. Once the plug is removed from the pole, take out the screw and thread it into the top of the plug. Then glue the plug back onto the top of the pole. The plug has a considerably larger diameter than the pole, which is a problem. Once the glue was set, I ground the plug down to the same diameter as the pole. Then oven, pvc pipe, hair spray and slide the grips on. Carefully cut a little window for the straps in the appropriate place. I wanted to replace the original straps as well, so I got GG straps. Back the screw out, slip the grommet for the straps in and tighten the screw. Voila! You’re set for many more happy miles! A few pictures follow.
Pre Project:

Once the original grip is removed:

Completed project!

Beveled 1/2″ pvc pipe used to expand GG grips to the right size:
