I've not done a brisket before (dying to) and my ribs take me no more than 2.5 hours. That's the time i find my St. Louis cut ribs are done with that perfect bite I love. I would imagine you could do the brisket first, then do the foil, towel, cooler method like pulled pork to keep it hot for the length of time it takes to cook the ribs. I've had my pork butt stay hot for 4 hours wrapping it that way when it's done.