Dogs naturally do swallow quite an amount of their own hair, through grooming, which does pass through with no problems, but I certainly would not let him eat large chunks from his brush, it could cause a blockage. I would stuff a ball or chew in his mouth whilst I were grooming him outside. It is a terrible time of year for moulting at the moment most of us are probably suffering with the excess coming off.
I groom my girl twice a day, sometimes more outdoors to try and limit the house being smoothered in her shedding hair. :-D