We were in Lake City just last week. Came over Slumgullion from the south. Going up was easy even with full load of 100gal water since the CG we were going to had not turned on their water yet. Drive by RPM. In my case, between 2000 & 2300, no matter the gear for best torque & no overheating.
Coming DOWN from Slumgullion, now that is another issue. Stay in low gear & don't ride the brakes. It is one heckuva long grade & steep. Trailer brake drums were quite warm by the time we got to the bottom but we never stopped on the way to let them cool like the time before when too much brake load was on the truck & we had to stop for smoking truck brake pads.
Drive to suit the conditions & your equipment. Don't worry about the line of cars that may build up behind. Too bad for them. They will have to wait. Better to go slow than try to drive like there is no trailer, crash, & close the road for everyone.