Just wanted to give a little update.
I'm probably going to start her as far as I can by myself first. I'm not really in any rush so we will take our time and have fun with these new training exercises. I will definitely get a professional to evaluate her before hooking her to a cart though.
I do know one person who trains show horses to drive so he is giving me a few pointers. If I get stuck with anything I can ask him. Although I am still going to need to find someone to give me some lessons. He only drives his horses in the arena and right now all he has is babies who are being saddle broke.
I went ahead and got some blinkers to introduce my mare to them. She really didn't react at all. I put them on and off a few times and then I lunged her with them- it was weird for me because I couldn't really watch her eyes like I am used too. She was really good- all she was thinking about was how quickly we could get done so she could go back to grazing. Every time I said whoa she tried to steal grass.
I dragged a small pvc pole over and she had no reaction to that either. I waved it all over in the air, rubbed her all over with it, dragged it next to us while walking... Again no reaction. I went ahead and tied it loosely to the surcingle and ground drove her at the walk. She was perfect. Every time the pole fell out of the tie (I didn't tie it solid), she would just stop and stand there. I obviously wouldn't have gone that far if she had showed any signs of nervousness.
The only bad habit I think we will need to work on is that she wants to stop and face me when I say whoa. My fault because I did some Clinton Anderson training with her, and I always wanted her to give me two eyes. Her turning isn't as responsive as it is under saddle so we will be working on that too. She still needs to be introduced to the crupper.
The crupper might be a problem, hopefully not. She seems to have more of a problem with excess energy (from being worked so inconsistently) rather than really being upset by anything.
It will probably be 6 months or more before I buy a cart or harness. That gives me plenty of time to play around with her, find an instructor, get lessons etc. If all goes well that is!
If nothing else all this desensitization will just give me a better riding horse.