First, I buy a 10-13lb packer brisket. I choose the most flexible one available and choice or prime is best.
Trim fat off of meat to an even thickness. About 1/4 inch is fine.
Cut up a large onion in chunks. Add onion, One 12oz beer, and one bottle of Hot and Spicy Allegro. Dump all three into a large alum pan. I prefer Shiner Bock and the Allegro can be found at HEB in Texas. I'm not sure about other states.
While sitting on a cutting board, cover all exposed surface of meat with yellow mustard and then your rub of choice. I normally use a rub made of equal parts garlic powder, sea salt, and fresh ground black pepper. My last brisket, I used a rub called Grand Champion. The Grand Champion was superb and I will use it from now on. Place the seasoned meat in the pan with the stuff listed above.
The meat goes directly into the pan resting in the liquid and onion. Use a platesetter, legs down and the factory grate. Place pan with brisket on top of the grate.
Stabilize egg at 300 dome temp. Add 6-8 fist size chunks of hickory or mesquite or both. Let the egg sit for 20-30 min to burn off any nastys in the wood and lump.
Once the brisket reaches 205, check for tenderness and remove from egg. (I've never had one not be tender at 205 but, I've heard it happens) Save the liquid in the pan for sauce.
Be careful, man! I've got a beverage here.