In a large bowl, add chicken pieces, buttermilk, pickle juice, hot sauce and salt. Use hand or spoon to mix together. Cover and refrigerate for at least 2 hours, or overnight.
To prepare the flour mixture, in a shallow dish, thoroughly mix all-purpose flour, corn starch, sea salt, seasoning salt, garlic powder, onion powder and paprika. Remove a chicken piece from marinade and toss chicken in flour until thoroughly coated. Place on a rack. Repeat with all chicken pieces. Let coated chicken sit for 15-20 minutes before frying.
Preheat oven to 225 degrees.
Fill a large cast iron skillet a little over halfway with vegetable oil. Over medium-high, heat oil to 350 degrees. Carefully place chicken into hot oil, skin side down. Do not crowd pan. I typically do 3-4 pieces at a time. Fry for 8 minutes on each side, or until chicken has an internal temperature of 160 degrees. Place chicken on a clean wire rack and baking sheet. Repeat until all pieces are fried. Reserve 1/2 cup of the cooking oil. Place chicken in preheated oven to ensure chicken remains hot and crispy while you prepare the sauce.
To make the sauce, in a medium saucepan, add butter and reserved cooking oil. Add cayenne pepper, paprika, brown sugar, garlic powder, onion powder, salt, and chili powder. Heat over medium heat. Stir together until all of the oil is melted and everything is mixed. Turn off heat, but cover to keep sauce warm.
Remove chicken from oven, and brush on both sides with the sauce. Serve hot.