My horse is the same way. Just buckle the girth hole by hole on either side. It should help him to stop moving. He might still act out when you put the girth in the hole at first. Just keep him calmed and walk him in a circle. But you can't stop a horse from not liking the girth/cinch altogether, so I hope this helped in the slightest🙃
First thing is first - ask yourself why your horse is girthy. Is he sensitive around his stomach? Does his saddle pinch him due to incorrect fitting? (most likely the issue). Are you maybe tightening your girth too much too quickly, causing him to react?
If you know there are no underlying problems such as these, do the following:
- Slowly tighten your girth
- If he turns to nip, do not stop tightening the girth. Instead, tighten it quickly and only soften it when he turns away.
- When he's standing nicely and not trying to nip you, slowly tighten the girth and reward him if he does nothing.
If you repeat this process, he will soon begin to associate trying to nip you when you're tightening or fastening the girth with receiving more pressure.
Be patient and this will work! :)