Should be no biggie, here's my trick for handling hills (Mont Eagle anyone?)
Soon as you crest or start heading downhill downshift, I like matching my max speed to just short of my max RPM. My redline is 3200 so I don't let it exceed 2800, which is 4th gear at 60 IIRC. Being a gasser your redline is likely 6,000, so I'd go no higher than 4,500-5,000 or so.
If the grade is shallow enough that engine braking will maintain your speed, awesome! Never let it get away in the first place.
But what if you can't be in a lower gear and maintain a decent speed? The slope is too great, the gearing doesn't match just right.
If the limit is, lets say 55, and the engine isn't holding the speed down, it's creeping up faster and faster. Then I'm going to let it coast up to 60ish then use the brakes to pull it down to 50 or so, then off the brakes and let it coast up to 60 again, then brake down to 50 again. The engine braking maintains about 70% of your speed, using the brakes on occasion takes care of the remaining 30%.
Why do that? If you drag the brakes to control speed, even just a little, they will build up so much heat that they'll glaze over, boil the fluid, and before long you have no brakes.
But by using the brakes sporadically to scrub off large amounts of speed, the time where the brakes are off and it's building speed back up the brakes are cooling off.
Plus they build up less heat during the slowdown process meaning that you're all the safer.
In short, you should be fine simply downshifting. But if you find your speed creeping up then you can use the brakes to pull it below your desired speed and let it slowly build back up while the brakes cool off.
But, if you're still having an issue maintaining speed then as OC said slow down to a speed that you can safely maintain. Folks will get over you going slow in the right lane, they won't forgive you for tangling them up in a preventable crash.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10