The generally published process is as follows:
If your controller has light and heavy options, set to light if your trailer weighs less than your truck. Set to heavy if your trailer weighs more than your truck. Somewhere where you are comfortable driving and stopping in the absence of traffic (there will be no brake lights) set your brake controller to some nominal gain, higher the greater your trailer weight. While driving at 25 mph apply the trailer brakes lightly with your brake controller lever or knob several times for a few seconds to warm the brakes up, then apply full trailer brakes and listen for the sound of skidding tires. If the tires skid, turn the gain down until they don't. If they don't skid, turn the gain up until they do and then back down until they just don't.
This process will give you the maximum available braking power from the trailer.
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins