My commute has me coming down out of the mountains to the plains and climbing again in the afternoon, so I understand your situation.
There's no painless way of climbing hills, you can only experiment with different speeds and gears to see where your vehicle returns the least fuel consumption.
On the plus side, you use a lot less (if any) fuel going down those same hills, so the two directions average out to a more reasonable FE figure.
Others have already noted that DFCO can work for the down hill section, but can be limited to certain rev ranges that aren't always practical to maintain.
I use an injector cut-off switch so I can leave the car in 5th, 4th or 3rd gear (depending on how steep the hill is) and keep near the speed limit while using no fuel.
For the tight curves at the bottom of those really steep hills I supplement engine braking with the foot brake as required. I always have full brake booster vacuum (and power steering) due to the engine braking.
My injector switch is a maintained push button mounted on the gear stick, that operates a relay in the engine bay.
It works for me.
