Thaw frozen Whole Turkey (12 pound) in refrigerator for 5 days; check cavity for neck/organs (discard or save for making stock).
Bring 2 quarts of Water (2 quart), Caster Sugar (2 cup) and Cajun Seasoning (1/2 cup) to a boil in a large pot over medium high heat. Stir to dissolve and pour into gallon pitcher.
Add Salt (1 cup), Garlic (6 clove), Celery (2 stalk), Onion (1), Bay Leaf (4), Black Peppercorns (1 teaspoon), Fresh Herbs (1 bunch), and Lemon (2) along with Water (2 quart) and steep for 1 hour or until mixture cools to room temperature.
Pour over turkey and add remaining Water (2 quart) to completely submerge turkey in the brine.
Place turkey in an XXL Ziplock bag and pour brine over bird. Store in a cooler with ice around the bag to keep cool. Brine Turkey for 24 hours replacing ice as necessary.
Prepare smoker for indirect cooking at 300 degrees F (150 degrees C) using pecan wood for smoke flavor.
Remove turkey from brine and rinse under cool water. Pat skin dry with paper towel.
Place Chicken Broth (14 fluid ounce), Butter (1/4 cup), Killer Hogs Hot Sauce (2 tablespoon) and Cajun Seasoning (1 teaspoon) into a bowl or mason jar and whisk to combine. Shake or stir well before injecting.
Place quartered Apple (1) and Onion (1) in the cavity and tie the legs together with butcher twine. Inject the breast, legs, and thighs with Cajun injection. Coat the skin with vegetable cooking spray.
Combine Killer Hogs The A.P. Rub (1/4 cup), Paprika (2 tablespoon), Dried Oregano (1 tablespoon), Dried Thyme (1 tablespoon), Onion Powder (1 tablespoon), Dried Parsley (1 tablespoon), Cayenne Pepper (1/2 tablespoon) and Ground White Pepper (1/2 tablespoon) and store in airtight container for up to 1 month.
Season the outside of the turkey with Cajun seasoning* and place on preheated smoker.
Smoke the turkey for 3 ½ hours spraying the skin with additional cooking spray as necessary. Remove the turkey from the smoker when internal temperature reaches 165 degrees F (73 degrees C) in the breast and 175 degrees F (79 degrees C) in the thigh.
Cover turkey loosely in aluminum foil and rest for 20 minutes. Carve into desired portions.