Thought I better post a follow-up and report on how things went, just in case someone searches and finds this thread.
First, thanks for all the help, both in the thread, and PM's. You guys gave good advice. Unfortunately, I'm not a cue maker, or even a repair guy, so I don't have some of the equipment. I do work on my own stuff, and occasionally will do something small for friends.
Having said that, the work was very successful. His cue ended up at 11.9mm making him very happy--and emboldened by that, I took one of my own from 11.5mm to 12mm. For his I used thin coats of spray poly bought at Wal*Mart.

For mine I used a foam brush and an old can of poly. The poly in the can was crusty, which proved to be beneficial, since it went on thick and dried fast. Both required some sanding and polishing.
I like the feel of the shafts...they are silky smooth, but don't feel sticky. I don't sweat, so if you do, you might not like the feel without talc.