Make Brine: In a medium pot, combine 2 cups warm water, salt, sugar, lemon thyme brine and the cattle prod. Heat until dissolved. Remove from heat. Stir in 2 cups cold water. Cool to at least room temperature.
Brine: Remove the turkey from the packaging. Discard the organs, neck and pop-up thermometer, if it has one. Place two brine bags inside of a bucket. Place the turkey in breast side facing down. Pour the cooled brine over the turkey. Add more cool water to fully cover. Tie the inner bag in a knot, pressing out as much air as possible. Place the bucket in the fridge for 8-12 hours.
Air Chill: Remove the turkey from the brine. Set it on a rack over a rimmed sheet pan. Pat it dry. Place the turkey in the refrigerator uncovered for 2-4 hours. This will remove excess moisture.
Season: Cut the butter into five pieces. Place 1 piece under the skin of each breast. Place 2 pieces inside the cavity with the vegetables and herbs. Split the last piece in half and tuck one half into each thigh socket. Season all over with turkey rub.
Heat Grill: Heat the drum smoker to 275-300F degrees with lump charcoal and wood chunks.
Smoke: Place the turkey on the smoker breast side up. Smoke for 2 1/2 hours.
Baste: In a bowl, combine the melted bacon grease, whiskey and soy sauce. Once the turkey has started to turn golden brown, brush the glaze all over the bird. Continue smoking until the turkey thigh reaches an internal temperature of about 180F degrees.
Rest: Once the turkey is ready, close all of the vents on the smoker to extinguish the fire. Allow the turkey to rest, until you're ready to serve it.
Carve: Serve the whole turkey on a bed of fresh herbs on a platter. When ready to carve it, remove the legs and wings. Carve off the breasts and slice into 1/2-inch thick pieces. Pull the remaining meat and arrange on the platter without the bones.