Whisk salt into buttermilk in a shallow baking dish. Add chicken, turning to coat. Cover and refrigerate, allowing chicken to marinate at least an hour (up to overnight). Bring chicken to room temperature before frying (that means taking it out of the fridge 30 minutes prior).
Meanwhile, add all ingredients for coating into a large zippered freezer bag and shake to combine.
Heat oil in a deep fryer to 350ºF, or 3/4" deep in a large cast iron skillet. Line a baking sheet with paper towels and place a wire cooling rack on top.
Remove chicken a piece at a time from the marinade, letting excess drip off. Add chicken to the bag with flour mixture and shake to evenly coat. Cook chicken in two batches, flipping once, until golden brown and cooked through (165ºF internal temperature), 8-12 minutes. Transfer to wire rack in a single layer. Serve hot, or cool completely on the wire racks before refrigerating.