Also very helpful during crisis periods: Cranberry juice.(much easier to get than GCG and just as effective. Or even more since there's no amount limit).
Above all, tell him to avoid eggs and fatty foods!!! They're the number one trigger of gallbladder attacks, eggs in particular, and to monitor his diet for his reactions to other food items such as dairy and spicy stuff. In one study eggs brought on attacks to almost 90% of those studied !!!