Thank you all for the wonderful, supportive comments yesterday. And of course I'm always happy to hear how handsome my horse is. :)
I didn't have much time tonight, but we had fun anyway. We went back over how it feels to have a rope around your butt, then I got an itch to hook up two reins and "drive."
My two reins were short because they were actually a lead rope and a riding rein, but they did the trick and I didn't have a bunch of extra driving line to deal with. I had no worries that he was going to kick me. I worked my way rearward, slowly transitioning back from a lunging position. He was ready and waiting for some kind of cue, so I asked him to turn, which pushed his hindquarters in front of me and caused him to switch sides. That made him feel pretty insecure so we took a little breather and just relaxed for a few minutes. When we tried again, the first thing he offered was a slight turn, switching sides in front of me. He sure does try his heart out to do the right thing. I hadn't asked for it but that's okay.
We did some more just moving around, switching sides, and even a couple stops. Then I took pictures of his butt, because wouldn't it be a very nice arse to sit behind while driving a cart?
Another goal I have is to pick out his feet daily. They don't actually need it because it's so dry and nothing packs in there, but he is so bothered by hoof trims that I think he definitely needs it as a training exercise. He behaves himself very well for a trim, but it's obviously quite a trial for him.
Something has definitely changed in our relationship lately. I like it a lot. :)