>>>use the position of the locknut to set the adjustment and the adjustable race to lock things down<<<
I can back Tom up on this tip. I've been adjusting head sets this way for years. No one showed me, I just sort of stumbled on it. It takes a little practice, but once you have the feel it works quite well. I position the wrench on the race cup close to the wrench on the cap nut so that I can "pull" the race into the cap nut while keeping the cap nut stationary. I also support Dave's suggestion of using something other than a conventional HS wrench for the top nut. A large crescent or a six point box-end wrench (if the top nut is hex) work pretty well.
Always looking for a way to minimize the marring of HS bits. Over the years, I've run across some that are pretty thrashed.
Wayne Bingham
Falls Church VA