Me. I use what ever gear it takes to hold the speed I want. Often coming down from the Blue Ridge, That is first gear. then I can shift to 2nd as we get down to the less steep, and less twisty sections. General rule is to use the same gear coming down you use going up. But if you need more, drop another.
Also even thought you may worry about your tranny. Using it will not only save your brakes, but may save your life. IF you heat the brakes too much coming down. You lose them all together, and then it will be too late to gear down. You will just be along for the ride. So for safety. Use the trany. I can come 321 from Blowing Roch, and down 16 from Glendale Springs, and hardly use the brakes.