Pearlsasinger
Up in the clouds
Without seeing the horse, it is difficult to say whether it is a pain issue or simply bad behaviour. I would make sure that the rug fits well, that it is being put on BHS style, without nipping the horse in any way (no throwing the rug at the horse's back but making sure that it is folded and 'placed' on the horse).
Then, when I was sure that there is no excuse, I would smack the horse, preferably making a loud, discouraging noise in the process.
I have a horse that threatened to bite when I got her, I knew that it was because of previous experiences, when people had been rough in tacking up. I cured this by rewarding her for good behaviour and ignoring the bad but I have certainly smacked those who were just doing it to be boss and would again.
Then, when I was sure that there is no excuse, I would smack the horse, preferably making a loud, discouraging noise in the process.
I have a horse that threatened to bite when I got her, I knew that it was because of previous experiences, when people had been rough in tacking up. I cured this by rewarding her for good behaviour and ignoring the bad but I have certainly smacked those who were just doing it to be boss and would again.