Add to a pot the salt, brown sugar, and 2 cups of water. Warm over low heat until all the ingredients are dissolved.
Add the warm liquid to a large bowl then add the ice and cold water, stir to combine then add the butterflied chicken. Leave to brine for 2 hours.
Garlic Butter
In a bowl combine the rub, softened butter, granulated garlic, and fresh finely diced garlic. Stir while pressing the seasonings into the butter, continue until the ingredients are well combined. Leave for the flavors to infuse.
To Cook
Preheat your smoker or closed grill to 300 degrees F ( 150 degrees C). If using a Gateway Drum Smoker set the grate on the middle rack. Also, heat the brick or skillet that you plan to put on top of the chicken to flatten.
Loosen the skin of the chicken by running your fingers under it around the breast and thighs then start stuffing it full of garlic butter, using about half of what was made. Use the remaining garlic butter to rub on the bone side of the chicken and on the outside of the skin.
Remove the heated brick or skillet. Place the buttered chicken skin side down in the center of the preheated smoker then top with the brick or skillet. Cook for 45 minutes.
Remove the bricks or skillet and flip the chicken so now skin side up. Continue to cook until 160 degrees F (72 degrees C).
Combien the BBQ sauce and apple juice to get a coating consistency. Apply this to the skin side of the chicken and cook for an additional 5 minutes or until the glaze sets.
Remove from the smoker then rest for 5 minutes before serving.