On descents, you want to go SLOW. Keep your speed down to no more than 35 mph. 30 is better. Engine brake ON. Lower gear if necessary. Flashers ON.
If your speed creeps up to 35, brake for a few seconds to get back down to 30.
The point is that if you let your speed get up to 40 or 45, you'll be doing a lot of braking to get under control for the next curve. And if your brakes aren't in tiptop condition, you may not be able to control your speed at that point.
Going up the mountain, it's easy to get stuck behind a very slow heavy vehicle. Once that happens, you'll usually be trapped because traffic in the other lanes will be moving much faster. So while in the right hand lane, if you're able to keep your speed up with traffic, keep your eye out for slow moving vehicles ahead of you and give yourself plenty of time to change lanes to get around them.