breaks

My understanding has always been that you spin the wheel and tighten until the wheel won't turn. This centers the shoes. Then back off until there is a slight drag. You can test your brakes various ways. The simple way is to roll along about 25-30 mph in a safe place with no traffic and apply them with the manual override on the controller. You should feel significant stopping effect. I you're on gravel, the wheels should lock up and slide. On pavement,, ideally, they would be right on the threshold of lockup.

This won't give you information about each individual wheel but will give you a good idea if your brakes are working. While adjusting, since you have the wheel off the ground, you can have someone use the manual lever on the brake controller and see if the wheel locks up. If you don't have a helper or you aren't hooked to the TV you can pull the brake away plug long enough to check each wheel. If you're nervous about leaving the plug out put it back in after checking each wheel and pull it again after you go to the next one and are done adjusting it Just don't for get to plug it back in.

If you go to the Dexter axle website, they have a section in the manual on brakes on adjustment.