Whisk the buttermilk, hot sauce and 1 teaspoon salt in a large bowl, add the chicken and refrigerate for 4 to 12 hours.
Remove the chicken 30 minutes before frying, then whisk the flour, paprika, garlic powder, black pepper, cayenne and remaining salt in a shallow pan.
Lift each piece from the buttermilk, let the excess drip for 5 seconds and press it firmly into the flour until no wet patches remain.
Rest the coated chicken on a rack for 15 minutes so the flour hydrates and clings.
Heat 3/4 inch oil in a 12-inch cast-iron skillet to 325°F and arrange half the chicken skin-side down without crowding.
Fry for 7 to 9 minutes per side, adjusting the burner to keep the oil between 315°F and 330°F, until deep golden and at least 165°F beside the bone.
Drain on a clean rack, return the oil to 325°F and repeat with the remaining chicken.
Rest the fried chicken for 8 minutes before serving so the juices settle and the crust firms up.