One thing that I have learned about dogs is that their own barking can make them worse.

My ex-friends rottie was NUTS, crazy & aggressive... He was a totally new dog when muzzled. His own barking use to make him madder & madder, but when he couldn't bark, he chilled out.. a lot. THen after several months he didn't need the muzzle.. but for safety we kept it on him during walks, as he could never be fully trusted.

It wouldn't hurt to give it a try. Try to find one that wont allow him to bark, but STILL drink! Also try to find one that wont come off with ease.

Get your brother to put it on him & give him lots of loving. Take it off & give him a treat. Do that for a few days until he sees the muzzle as a happy fun thing. Then get him to leave the house for 5 mins & come back. then 10, 15, 20 & so on (if possible).

Hopefully within the first week, the muzzle will be on him while your brother is at work. Also becuase of the muzzle not allowing him to open his mouth wide, it'll help keep the house in order...

Yes the dog is going to be bored during the day, but it wont be a forever thing. & at least he can run around the house & chase a ball on the floor (leave some balls out).

Hope that helps