Generally, I just get the lines buttoned up and let the pump run. If it runs too much... well it is not my electricity... <grin>
I use my trusty YJ 69075 micron gauge... been using it for 6+ years. Had to replace the sensor once... they do not like being hit with 100#+ pressure when you open the service valves (tired after a long day).
Good tools and good service practices... means good work and happy customers... which means referrals!!!