I began by immersing the grips in clean acetone for 10 minutes or so. You can see the old finish start to wrinkle up, then start scrubbing with the toothbrush within the checkering. After cleaning the checkering i started cleaning the smooth area with 000 steel wool. Once all the finish was removed I dried and wiped any excess acetone and visually inspected for any remaining finish. I let the grips dry overnight even though the acetone drys pretty quick. I prep sanded the grips with 1000-1500 grit paper, then removed any remaining dust with an air chuck. I then did a quick wipe down of the grips with acetone again. I opened the polyurethane and started with the checkering by carefully applying with a clean toothbrush. After the checkering was completed, I used cheesecloth to finish out the smooth areas. Take it slow and move in the direction of the grain.
I decided to go with the polyurethane instead of the spar urethane. I also took advice from another forum member on hand application vs spray can. It was solid advice. I feel pretty good about this system. It was definitely easier than I anticipated.