Sprinkle the rub on all sides of the tri-tip. Leave at room temperature for 30 minutes.
Light your coals with a chimney starter. Let burn for 10-15 minutes. Dump into the basket of the Barrel House Cooker. Set the intake to your altitude setting. Set the barrel onto the base, and let the coals burn for another 5-10 minutes with the lid open. Place the H-frame in the cooker.
Pierce a hook through the thick end of the meat about 3 inches down from the end. Hang in the cooker, and close the lid.
Cook until the meat reaches an internal temperature to match your desired doneness. For medium rare, cook to 120. For medium, 130. For medium well, 135. For well done, 145. The final steps will add 15 more degrees to the internal temp.
Remove from the cooker. Remove the hook and set aside.
Remove the barrel from the base of the cooker and set aside. Place the open frame over the coals in the base of the cooker and add the half grates. Let heat for a couple of minutes. Add the tri-tip to the grill. Grill directly on the grates about 3-5 minutes per side.
Remove. Let rest 10 minutes. Slice and serve.
For even more flavor, rub the tri-tip and let it rest covered in the fridge overnight. Set it on the counter to come to room temperature when you light your cooker.