We worked, still at the walk, on more strengthening of the right hind - lots of stepping under and into the corners and turns, and some spiral-out work while going to the right. I could tell it was somewhat hard work for her, since she started out somewhat bracey when we began our work on this, but she improved as we went. She pretty much stays soft continuously at the walk now, without any curling up or going too low. This means that I now have a pretty clear idea of when she's struggling a bit with something because the brace tends to come back until we work through it.
In order to "sneak up" on halting without bracing, and in lines with Jean's very good suggestions from a couple of posts ago, which were in line with what I was also thinking, we did lots, and lots, and lots of transitions within the walk from long-strided, marching walk to shorter-strided walk, while keeping the same tempo. I did this without any hand or leg aids at all - just either "allowing" with my seat to get the longer strides, or slightly resisting the motion with my seat to ask for the shorter strides. We also worked on maintaining the impulsion regardless of stride length and on keeping the same tempo - so the shorter steps weren't slower, we were just covering less ground. She picked this up very quickly, as we've done some of this work before.
While I was grooming, and while I was untacking and giving her a rinse off in the wash stall, I asked her to ground tie. She did beautifully, and one of the boarders said "my horse could never do that" - this is a pretty traditional hunter/jumper barn where horses are always cross-tied. I told her that Maisie had always been a very fidgety horse until we worked on some patience and self-calming exercises. They probably think I'm a bid odd, and perhaps they're right!