Mix the buttermilk, hot pepper sauce, and 1 teaspoon of salt in a container that will hold all of the chicken. Add the chicken parts, turning to coat them well. Cover and refrigerate for at least 2 hours and up to 12 hours, turning occasionally.
For the flour coating, combine all of the flour, cornstarch, and seasonings in a large brown paper grocery bag or large plastic bag (set aside 3 Tbsp of mixture for gravy if making). Drizzle about a tablespoon of the buttermilk mixture into the flour...yes, small lumps are OK!
Position a wire rack over paper towels for draining the chicken near the cooking area.Heat the oil in a 12-inch to 14-inch skillet over medium high heat. If using, add the bacon drippings to the skillet. When the oil reaches 375°F, reduce the heat to medium and begin to prepare the chicken. Pull the chicken pieces, one at a time, out of the buttermilk and let any excess liquid drain back into the bowl. Drop a couple of pieces of chicken into the seasoned flour and shake the closed bag to coat it. Make sure plenty of the flour mixture coats each piece of chicken, including those little lumps (those will become delicious crispy bits!)
Place each piece in the skillet, skin side down. Only fit as many pieces as will fit together in a 12-inch skillet, close but not touching. (For my 5 thighs and 6 legs, I had to do two separate processes to cook all pieces).
Adjust the heat as needed to maintain a temperature of about 300°F (adding the chicken to the oil will drop the temperature to this already) and fry for 15 minutes.
After the allotted time, turn the chicken. Best to use tongs to avoid piercing the crust. Put a lid on the skillet and fry covered for 13 to 15 additional minutes, until the crust is a rich golden brown and the meat is cooked through but still juicy.
Turn up the heat to medium high and heat both sides just enough to get a nice brown and crisp up the crust. Check the interior temperature; for light meat it should be no higher than 165°, I like to cook dark meat longer, up to 175°, it won't dry out and pulls away from the bone easier. You can actually remove the meat prior to it meeting those temps by a couple of degrees; it will continue to cook for a few minutes after it's removed from heat. If it meets that temperature, drain the chicken on the rack; skin side up.