Great post, Calamity Jane. I agree completely. I have found that the things you mentioned work in most situations, but sometimes my horses just need a little reminder that they can't "have their way" - even when my focus is on moving away from the barn, and my cues are solid.
I have found that occasionally my horses will pull an act along the lines of, "I don't want to go and you can't make me." This usually happens if I have been away from the barn for more than a few days.
Daisy will just turn around and walk towards the barn when I ask her to move out.
I have had GREAT success with turning her in circles in the same direction she's trying to turn - make her attempted 180 into several 360s. I make turning around MY idea. As soon as she realizes that turning toward the barn didn't work the way she planned, she stops. She also can't fight me or pull on when she's bent around my leg turning in circles.
I have found this tactic quite useful: make the right thing easy and the wrong thing hard.
Calamity Jane is right that you have taught her a very bad habit by dismounting and leading her away. She has learned that when she fights you, you get off.
You need to stay on her back no matter how long it take for her to figure it out. Stay confident, remain secure in your seat, and set your mind to moving on. If your horse thinks for one minute that she's got you, she isn't going to stop.
Simply make what she wants more work, and what you want easy - turning in circles is hard; walking away is easy.
Hope this has been helpful.