I lived on the West slope of Colorado and worked in Denver. I have been over the divide well over 800 times. Lizard Head, Red Mountain, Wolf Creek, etc. The goal going up is to not over heat the engine or transmission. The goal going down is to save the service brake for an emergency stop, that is never touch them. Gas engines and diesel engines have different Brake HP for the same displacement. Keep your RPM slightly below peak HP with less than full throttle, use the transmission to select a gear that does that while keeping temps in control. Going down, select a gear that allows you to not use the brakes. That gear will on or two lower than what you came up on.