Muzzle rubbing and also enabling bullying in field?

[Schoolrefusa]

Hi,
we keep our horse at livery and they are all out at this time of year which normally is really happy . However with so much grass we have to restrict ours and even a flexible muzzle (a good brand which claims not to rub) is rubbing as is their breakaway head collar and really upsetting him .
To make it worse he is also being bitten and chased around as can't stand up for himself so easily with a muzzle on to fight back !
does anyone have any advice? I've found sheepskin pads for the head collar I'm ordering but still worrying.
thanks so much

My mare normally wears a Greenguard muzzle attached to leather head collar
It always rubs her chin to start with, so I normally plaster her chin in sudocream... it hardens up eventually after a week or two
Add sheepskin if makes you feel better, just be aware it can change the fit - so may rub elsewhere...
No help with the bully though, my mare is a loner and has a glare that keeps most others away 🙈