I would cheat the brisket put it on let is go 6 hrs. pull it wrap it (Preferably in Butcher paper) and put it in the oven to finish. Do the same with your but & use foil on it. Cook both to probe tender(the only spot on that brisket that matters is th thickest part of the Flat, if it is probe tender the rest will be perfect). I recommend this because it will give you better odds of success especially cooking for a crowd, Hone your skills on your family not your friends.
I'm a Proxy Vegetarian> Cows eat grass & I eat cows.