Cornell method:
https://whatscookingamerica.net/Poultry/CornellChickenBarbecue.htm
http://www.atlasobscura.com/articles/cornell-chicken-barbecue-sauce-upstate

Cornell Chicken Barbecue Sauce

1 cup cooking oil
1 pint cider vinegar
3 tablespoons salt*
1 tablespoon poultry seasoning
1/2 teaspoon pepper
1 egg
Beat the egg, then add the oil and beat again. Add other ingredients and stir. The recipe can be varied to suit individual tastes. Leftover sauce can be stored in a glass jar in a refrigerator for several weeks.
(Adapted from Cornell Cooperative Extension Information Bulletin 862.)

* Adjust the quantity or eliminate salt to meet individual health needs and taste. Barbecued chicken basted frequently during cooking will be saltier than chicken that has been lightly basted.

To Grill the Broilers:

Place the broiler halves over the fire after the flame is gone. Turn the halves every five to ten minutes, depending on the heat from the fire. Use turners or a long handled fork. The chicken should be basted with a fiber brush at each turning. The basting should be light at first and heavy near the end of the cooking period.

Test the chicken to see whether it is done by pulling the wing away from the body and using a meat thermometer. If the meat in this area splits easily and the meat thermometer reads at least 165°F in the breast and thigh, the chicken is done.