Walk Pirouettes are something that I struggle with, as I screw myself up into a ball and so Batialo does too.
The goal is to keep myself tall and open my inside hip, to allow Batialo to move around my inside leg, and use my outside aids to control the movement.
If you get stuck halfway, or if your horse steps out, using the squares can be a great way to help maintain control.
Think of a rectangle, and at each corner collect the walk and steer the horse’s shoulder around his quarters until you are at 90 degrees, and then move forward with control.
This will help the horse learn to be ready for your aid to move out, so he won’t take over, and also help you gain control of his outside shoulder.
More importantly, is the ability to collect the walk, and ask for inside bend, without going off the line you are on, so if you cannot do this then don’t start the pirouette.
Work on straight lines, asking the horse to collect the walk and bend to the inside, without losing the contact, or the line you are on!