Here's what I do, not that you have to follow.
When I see a small grade, I turn off the CC and use my foot. If she downshifts then, I let her and slow down so she doesn't pop to 4k+. 3 is the max I allow. If you can see the grade coming and you time it right, you can gain speed to help.
It's not a complete cure depending on the grade and it's length but I've achieved 8+ mpg towing a 3500lb towed.