You really want to measure anything related to playing in as close to playing position as possible. Even slight pressure from a neck rest or the peghead being on a flat surface will make the measurement less reliable.
James uses the method you describe, Roger, only he does it while sitting down and playing, looking down at the string.
Don, you've got a good plan for setting the action to where you want it.
Joey's instructions are the best for setup. Study them well and practice the adjustments. Just like playing, adjusting does take practice to master so be patient with yourself as you are learning.
A word of caution on nut adjustments. Only chage the nut if you have a fret buzz on an open string only - one that goes away once you fret. And do loosen the center anchor screw first else you will bend the baseplate and I'll know you don't read directions when you order a replacemnt
