I started buckling down on Elsie's heeling last week. When she's on, she's GORGEOUS. But, unfortunately (because I'm lazy) she'd heel reliably for about a minute before wandering.
So, now I'm working on making heeling super rewarding to her, and on extending the behavior for a lot longer period of time.
She's already getting snappier.
Oh and I've been trying to get her to 'spring off the line' as it were, because she was lagging a bit on the first couple steps no matter what else I tried, so I'm trying to make jumping up as soon as I say lets-go (rather than waiting until I've already taken a step) part of the behavior, and so far that's working well, too.
I'm also actively seeking out more distracting environments for us to practice heeling in, because we both need it.