Brisket will be whole?
I prefer reheating brisket whole. Cool well after smoking; wrap then chill. I reheat on a rack in a roasting pan or on a sheetpan, brisket drizzled with saved foil juices or with a little stock mixed with a touch of butter, tightly covered, 300 oven (or cooker), till the internal is 145-150, tops. Higher than that and it starts cooking again.
I add a finishing sauce to pulled pork when pulling (not a serving sauce). Cool, then wrap and chill. For reheating it goes in a roasting pan, tightly covered, 300?. After 25 min or so I stir, recover, then stir every 10 or so till serving temp.