I've read that too but I wasn't sure if I'll be ok on auto :P
4low is definitely overkill but I wasn't sure if I should manual switch to 1gear during the descent part . Never had a manual transmission car
You will not need or want hill decent when heading down. You'll be ridiculously slow and quickly have a lot of traffic behind you. As others have mentioned there are paved sections and tight switch backs which are not conducive to 4 low.
Use your paddle shifters and keep it in the appropriate gear that requires as little braking as possible (probably 1 or 2), you'll inevitably need to do some.
Also, its closed for the year. So you'll have to wait until spring.