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Most whole chickens are already enhanced; they've been injected with a brine solution. So there may not be a need to brine. Look at the package label, if it states something like "Contains or injected up to 5% with sodium phosphate,...etc.)" there is no need to brine - the percentage can vary. If it states "contains up to 5% water", and not other ingredients are listed it could benefit from brining.
I prefer apple, maple or pecan for smoke flavor. Chicken takes on a lot of smoke so you may want to start with 1:00 - 2:00 hours of smoke. Keep in mind each bisquette burns for approximately 20 minutes.
Smoke/roasting two 3 pound chickens will give off a lot of moisture, so you should keep your vent wide open, at least during the first half to the cook. The process I use is to air dry them uncovered in the refrigerator for at least a couple of hours; 8 hours would be better. This helps improve the smoke flavor, and gives the skin a better texture. If you girl friend purchased this as a gift for you, you should ask her if she wants the chicken whole or spatchcocked (butterflied).
If you spatchcock the chickens they will cook faster, and take on more smoke, so if you spatchcock you may want to use the lower end of the smoke time. Too little smoke is better than too much. Too little you can always adjust the smoke time the next time. Too much smoke may be enough to make it inedible. As a side note, if I'm not looking for presentation, I will quarter the chickens and place the dark meat on one tray, and the white meat on another. That way I can take out the white meat when it hits a certain temperature, and continue to cook the dark meat.
I season with my favorite rub, and let them sit at room temperature for about an hour. During that time, I preheat the smoker to around 250°F, you can use a half opening on the vent to speed up the preheat time; just remember to widen the vent opening when you load the chickens. I will often finish them on the grill or preheated oven (450°F) at the end to crisp up the skin. As for time it's been awhile since I cooked chicken in the Bradley, and lost most of my notes. I go by internal temperature, and will measure the temperature at the thickest part of the thigh; 165°F; Cooks Illustrated recommends 175°F, for a better flavor of the dark meat.