When I adjust my trailer brakes using the brake adjust tool I just jack up the one wheel enough to clear the ground so I can spin the wheel.
If you are referring to the electric brakes those have to be done while in motion. My built-in brake controller doesn't respond to the brake pedal unless I am going at least 10MPH. I adjust my electric brakes going at least 25MPH and adjust to the point of sliding the trailer wheels than back off a tad. I am around a number 6 setting on my electric brake setup for my trailer.
Roy Ken