I use the tow/haul going up and down long grades, I do not leave it in cruise control, I have heard bad things about vehicles jumping out of cruise because of to much pressure on the transmission... Also If the pedometer start to sound I back off till it quits, your only hurting your engine if you keep pushing it past that point of no return ...
I going down the hill useing a lower gear than I went up the hill, not applying the brakes hard (never ever hold down on your brakes hard for length of time you will loose them going down a 6 percent grade). I Only apply my brakes enough to keep me at a slow speed an not over rev my engine or picking up any great ampunt of speed ...
Some of the grades out here in the western United States are 6 percent at 10, 15 and at times miles longer... If you keep hitting your brakes every few seconds or really hard you will loose them, trust me, I've seen it...
Do not be sacred of any of the mountain passes out here, if you use you head, think about what your doing you will be fine ...
Safe travels