Tow Haul + Cruise Control
Check your truck manual... I drive a chevy diesel. Its tow haul mode not only saves my truck engine (as others have already commented on), but also my truck and trailer brakes....
When going down steep grades: In tow haul mode I set my cruise control to an appropriate speed. Tow haul + cruise control automatically keeps me in the right gear for the grade. I don't have to ride my brakes.
When possible, I anticipate lower speeds needed on curves or hairpins... I'll start with a much lower speed so that when I get to reduced speeds on curves, etc., I still don't have to brake.
Tow haul is your friend!
Ann