Preheat your smoker to 225ºF-250ºF.
Trim the brisket’s fat cap down to 1/4”. Also trim any large chunks of hard fat from the edges of the brisket. Season all surfaces with R Butts R Smokin’ R Beef Rub. Rest the brisket until the rub looks wet, at least 10 minutes.
Transfer the brisket to the smoker. Smoke open until a dark bark is formed, 8-9 hours. Remove from the smoker. Wrap in butcher paper and return to the smoker. Continue cooking until an instant read thermometer inserted into the meat meets very little resistance. It should almost feel like probing room temperature butter. Total cook time will vary, but our 16 lb brisket took almost 14 hours, total.
Rest the brisket at least one hour, wrapped in the paper, before slicing. Slice across the grain.