Prepare 1 gallon of liquid chicken brine as per the instructions in the How To Brine Chicken article. Brine the whole chickens for 1 day and up to two days for larger birds.
Preheat your smoker to 225F - 250F. Try keeping the temperature closer to 225F. Smoke the chickens until internal temperature reaches 165F, about 2.5 - 3 hours.
Remove the chickens from the smoker and let rest for 5 minutes before serving.