I use the same controller. I find that what works best for me is to park it level, adjust the angle to where the light is barely on when stopped, then start playing at about 2/3 gain and adjust until they are just short of locking up....pretty much standard for all brake controllers. Once that's dialed in, I usually adjust on the fly with the angle knob and not the gain (unless it gets rainy or something like that).
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition