In a large bowl or baking dish, whisk together 1 quart of the buttermilk, 2 tablespoons salt, 2 teaspoons of chile de arbol powder, or hot sauce, and a little bit of pepper, if desired. Add the chicken pieces, turn to coat, cover, and refrigerate for at least 4 hours or overnight.
Place the remaining 2 cups of buttermilk in a bowl. Stir together the flour, garlic and onion powders, paprika, and 2 teaspoons chile de arbol powder (or cayenne) in a large bowl. Divide flour mixture among 2 shallow platters and season generously with salt and pepper. Drain the chicken in a colander and pat it dry. Dredge the pieces a few at a time in the flour mixture and pat off excess, then dip in the buttermilk and allow excess to drain off. Dredge in the second plate of flour and pat off the excess. Put the chicken pieces on a piece of waxed paper or on a clean platter while you heat the oil.
Pour about 3 inches of oil into a deep cast iron skillet; the oil should not come more than halfway up the sides of the pot. Put the pot over medium-high heat and heat the oil to 375 degrees F on a deep-fry thermometer. Working in batches, add the chicken pieces to the hot oil, 3 or 4 at a time and fry, turning the pieces occasionally, until evenly golden brown and cooked through, about 20 minutes. Remove from the oil with a slotted spoon and transfer to a rack to drain; repeat to cook the remaining pieces. Serve hot.