(1).In extra-large (2- to 2 1/2-gallon) self-sealing plastic bag, combine buttermilk, hot pepper sauce, and 1 teaspoon salt. Add chicken pieces, turning to coat. Seal bag, pressing out excess air. Place bag in bowl; refrigerate chicken 2 to 24 hours to marinate, turning bag over once. (2). In pie plate or bowl, stir flour, baking powder, pepper and remaining 2 teaspoons salt until well mixed. Remove chicken, a few pieces at a time, from buttermilk mixture, shaking off excess. Add chicken to flour mixture, turning to coat well. Place chicken on wire rack, set over waxed paper, without pieces touching. Repeat with remaining chicken pieces, using a second rack if necessary; let stand 15 minutes to set coating. Discard buttermilk mixture. (3). Meanwhile, preheat oven to 250 degrees F. Line two 15 1/2" by 10 1/2" jelly-roll pans or large cookie sheets with paper towels. Divide oil between two 12-inch skillets, preferably electric (there should be about 1/2 inch oil in each skillet), and heat over medium heat until temperature reaches 360 degrees F on deep-fry thermometer. (4). To each skillet, add 4 pieces chicken, skin side down, being careful not to crowd pieces. Cover skillets and cook until chicken is light golden brown on bottoms, 4 to 5 minutes. Turn pieces over and cook, covered (reducing heat to medium-low if necessary to maintain a temperature of 300 degrees F), 8 to 10 minutes longer for white meat, 13 to 15 minutes longer for dark meat, turning pieces every 4 or 5 minutes or until well browned on all sides and juices run clear when thickest part is pierced with tip of knife. (5). Transfer chicken to lined jelly-roll pans to drain. Keep warm in oven. Repeat with remaining chicken.