I've done multiple butts many times on a 22". I use the snake method with a large rectangular disposable aluminum pan under the meat. I add several inches of hot water to the pan to help regulate heat and add moisture. The pan creates a vey effective stop to build a large bank of coal around the circumference of the kettle. I typically fire the coals at the crack of dawn if we are planning to eat at 5 or 6. It often takes 8-10 hours getting the butt to 200 F (I've never cut them in half but would expect a faster cook if you do). I also like some rest time before I pull. I place my wood chunks all along the first long side of the rectangle. I don't add any more after that. I've had complaints of to much smoke on the past from the crew and this amount seems about right.
I do keep an eye on the meat as the burn reaches the turns. Coals are a little thinner at that point and I've had occasions where there was heat loss and the fuse burnt out. Also the meat will tend to hang over the pan at that point so I'll readjust the butts to keep the indirect. Hope that helps and good luck with the cook!
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