Remember what you are doing, centering the shoes to the axle. The arm (with dial indicator) pivots around the shoe allowing you to measure the distance from the center of the axle to different locations on the shoe. With the major and minor adjusters you move the toe or heel of the shoe in/out until you have the shoe entirely centered. Move the dial gauge to the location your adjusting and you can measure the amount needed to move.
The other piece to this process is you need to determine the max diameter of the drum with a drum gauge before starting the adjustment. Then set the shoes to that diameter less the clearance, typical .006. This way the drum will just slide on after the adjustment. It's actually a pretty quick process once you understand the objective, centering the shoes with .006 clearance from the drum. Couple other tips, make sure our drums are true, if not get them turned on a brake lathe. If the drum is out of round you will never get the brakes adjusted correctly. Lastly, I don't recommend the process mentioned in post #37. It will not give you anywhere near full braking capability. If you do that process , then adjust them correctly you will be very surprised by how much more braking capability you have.