1. Set the brisket in the freezer for one hour or more, after which it should be removed for trimming. Then, start the smoker at 180F, and as it heats, trim most of the fat cap leaving about a quarter of it. Ensure to cut off the hard fat, as it doesn’t render during cooking.
2. Combine the dry spices in a bowl and sprinkle them over the brisket. Ensure to pat it down so it sticks and reaches the entire surface. Then, wrap it in plastic and rest in the fridge for six to 12 hours.
3. Transfer the brisket to the smoker with the fat cap down, and stick the internal thermometer probe. Cover the lid and smoke the brisket for eight to 12 hours (preferably overnight), or until the internal temperature reaches 150F.
4. Increase the smoker temperature to 225F, and as the meat cooks, spritz it every 45 minutes to one hour with root beer.
5. Smoke the brisket at 225F until the internal temperature hits 195F to 203F and a sharp probe can slide into the meat without resistance.
6. Transfer the brisket from the grill into two layers of butcher paper and wrap it. Then, wrap it again in a towel, and keep it in a cooler to rest for one to four hours.
7. Slice the meat across the flat, and perpendicularly for the point.

This video can also help you with cooking brisket at 225F