Dunno if I can give you any help, especially since my wife's and my motto on the tandem is "We May Be Slow, But We're . . . Slow." When we are confronted with an extended grade, say 2 miles of 10% or 10 miles of 5%, we find that gravity puts us into the grannie pretty quickly and we just find a "zone" where we can get to the top while still breathing. Our combined age is 108 years, last year we put in 4600 miles and 222,000 vertical feet on the tandem, and we pretty much assume that our grannie will get the biggest workout in the hills. Just last weekend we sucked our chain and bent the grannie beyond use on one hill. After a hundred yards of being out of the saddle in the middle ring, we said the heck with it and pushed it up the remaining mile of that 11% grade.
So what am I saying? Maybe to embrace the grannie as your friend. And then to do as much climbing as you can, because the best way to get better at climbing is to climb. Earlier on the ride where we bent our grannie we went up a quarter-mile 17% wall that we could not have done two years ago.