Rinse chickens under cold water and pat entirely dry with paper towel. Rest atop a rimmed baking sheet and cooling rack, lightly salt, then place in the refrigerator for 4 hours, up to overnight.
2 hours prior to smoking, remove chicken from refrigeration and rest on the counter, returning the bird near room temperature.
Inject the bird across its wings thighs, legs and breasts with a combination of the stock, olive oil, butter and Beer Can Chicken seasoning. Drizzle with oil, then massage an aggressive amount of the Beer Can Chicken seasoning into all portions of the chicken.
Open a room temperature beer, drink (or discard) half the contents, then slide the whole chickens onto their respective beer cans.
Turn the smoker up to 375F. Once the smoke thins, place the beer can-stuffed chickens center-grates. Close the lid and roast for 60-90 minutes, intermittently rotating until internal temperature in the dark thigh meat reaches 160F and juices run clear.
Cautiously remove the chicken from the grill (attentive to the scolding metal beer can positioned inside the chicken) and transfer to a cutting board.
Rest for 10 minutes before discarding the beer. Carve, season additionally to taste, and enjoy!