This is a topic that gave me the cold sweats, but fortunately I've managed to avoid any white-knuckle moments, even dealing with some big/long mountain passes in Colorado and Arizona. Here' s what I do:
-Get a copy of the Mountain Directory
. I have a copy for the Western US that you are welcome to have. It's a big help for route planning and can give you some idea of what length and % grade to expect.
-Downshift at the top of the pass. You want to go down the hill in the same gear you came up the hill. And if you wait until you're carrying too much speed to downshift, your tranny might not be able to.
-Pick a target speed, which can be tricky because it really depends on the posted speed of the curves at the *bottom*of the mountain (this is where the Mountain Directory comes in handy). I'll use 35MPH as an example. I would let the bus get up to 40MPH, then use the brakes to get it down to 30MPH, then let off the brakes and coast (in gear, utilizing engine braking) until it gets to 40MPH, then use the brakes, etc. This gives some time intervals for the brakes to cool. Mind your redline on the tach.
-I use my hazards on downhill grades too, especially if I am crawling along relative to the other traffic.