From experience, I know that the longer you smoke anything, the better smoke flavour you will get.
Personally, I inject my meat first. The next thing is to maintain a temperature between 200°F & 250°F. I always check my wood and baste every half hour. I add coals every hour as needed.
With poultry, I remove it from the smoker while it is still a little undercooked and finish it in a covered roasting pan (with the rest of the marinade I used to baste) in the oven for about 45 minutes. This will keep your chicken or turkey from drying out.
I would smoke a 5 lb. chicken for 3 or 4 hours (130°F), then finish in the at 400°F oven until it reaches 170°F (approximately 45 minutes). It should turn out moist and full of flavour.