In a large bowl, add buttermilk, pickle juice and 2 teaspoons seasoned salt then whisk until combined. Add chicken pieces and make sure they are all submerged and coated. Cover with plastic wrap then place in the fridge to marinate for 2-24 hours (the longer the better).
When chicken is finished marinating, add flour, cornstarch, baking powder, garlic powder, onion powder, 2 teaspoons seasoned salt, black pepper and cayenne to a shallow bowl or pan. Stir to combine well.
Use tongs to remove chicken pieces (one by one) from the brine, place in flour mixture and turn to coat all sides. Once dredged, place chicken on a wire rack that's sitting on a baking sheet. Continue until all pieces are dredged. Place in fridge for 15-30 minutes. (crucial step)
While chicken is resting, pour 2 inches of oil in a large deep pot. Heat to 350° F. Use a candy thermometer or instant read thermometer to ensure the temperature stays as close as possible to 350°.
Carefully place chicken pieces using tongs into the oil. Do not overcrowd your pot because it will lower the oil temperature too quickly.
Fry until golden brown, turning as needed to brown all sides, then place chicken on a wire rack on top of a baking sheet in the oven on "warm" while frying the remaining chicken. Make sure the internal temperature of the chicken is 165° F before eating.