I prefer a smaller, centralized exhaust that I can close up easily to save the charcoal for the next cook. I've never used all of the charcoal in a smoke- even a 20 hour brisket. The exhaust size of a Weber kettle works well. On mine, I use 1/3 of a drum for a lid- the end with a 2" pipe bung. 2" pipe is actually a little big for an exhaust- I had to restrict mine a little to control temps. When done cooking, I close my intakes, remove the rain cap, and put a solid cap over the pipe. Fire goes out quickly.