Combine the buttermilk, 1/4 cup cayenne, 3 tablespoons each granulated garlic and paprika,2 tablespoons onion powder and 1 tablespoon sugar in a bowl and whisk until smooth. Add chicken and toss to coat. Cover and chill for at least four hours or overnight.
Drain the chicken, rinse and pat dry. Season with salt and pepper. Heat 2 inches oil in a 6-quart saucepan until a frying thermometer reads 300F/149C. Stir ¼ cup cayenne, 6 tablespoons granulated garlic, 6 tablespoons paprika, 4 tablespoons onion powder and 2 tablespoons sugar in a bowl. Transfer half to another bowl and whisk in the 2 cups self-rising flour.
Working in batches, dredge the chicken in the flour mixture. Fry, flipping once, until golden and almost cooked through, about 6 to 7 minutes or until an instant-read thermometer inserted in the thickest part of the thigh reads 150F/TKC. Transfer chicken to a plate lined with paper towels.
Increase oil temperature to 350 F/176 C. Stir ¼ remaining cayenne pepper and 6 tablespoons melted butter in a bowl until it makes a paste. Set aside.
Dredge chicken once more in the flour mixture and fry until cooked through, about 2 to 3 minutes. Drain briefly on paper towels and brush with the cayenne-butter paste. Serve with bread and pickles.