I've always used a Ford Wrench...it puts the pressure on the flats of the cap, not the corners. The fork caps don't require a great deal of effort to loosen...or tighten.
Dave
Purchased mine at Denver flee market 20+ years ago and have used it 2-3 times, need to drop front suspension to install chrome lowers and biggest socket I have is 1-1/4 so a bit short and would of had to pull/rotate handle bars. Great suggestion as old Ford wrench did the trick... again!!!