In a large bowl, whisk together the buttermilk, hot sauce, salt, pepper, and paprika. Add the chicken and make sure it's well covered. Refrigerate up to 4 hours, or overnight.
Prepare the Flour Dredge
In a large bowl, whisk together all of the flour dredge ingredients until well combined.
Cook the Chicken
Remove the chicken pieces one by one from the buttermilk and let any excess drip off.
Dredge each piece in the flour, shake off excess, dip back into the buttermilk, then into the flour again. Place on a rack-lined baking sheet. Repeat with all chicken.
Fill a deep fryer with oil, or fill a large cast iron pan about ⅓ of the way up the sides. Heat to 325°F.
Slowly add 3 or 4 pieces at a time and cook until golden brown and crisp on both sides, turning halfway through, until the chicken reaches 160–165°F — approximately 12–14 minutes.
Move cooked pieces to a rack-lined baking sheet and hold in a 250°F oven while you finish the remaining pieces.
Make the Hot Oil Sauce
When all frying is done, combine the cayenne, brown sugar, garlic powder, smoked paprika, chipotle chili powder, and red pepper flakes in a medium bowl. Add 1 cup of the hot frying oil and stir well to combine.
Brush the cooked chicken generously with the sauce, or dunk the pieces. Serve hot.