How we push a 6,000 ft. drop.
A road we take many times is from Flagstaff, AZ to Phoenix. Flag is close to 7k, Phoenix about 1K. At the beginning, I slow down enough to get into 5th, but don't lock it, then hit the retarder on and off during during the drop. Very seldom, do I have to hit the mains, unless you are in front of me and have geared-down too much. If there is a secret, as soon as one sees the "warning, steep 6/7% grades ahead", get the coach into 4th or 5th, toggle the retarder, and as the Eagles say, "Take It Easy". 
If you come blowing by me, no problem, but I'll pass you on the hills, and I'll watch your brake lights being on all the time on the next drop.
Topic: How we push a 6,000 ft. drop.