Preparation Mix 10 cups water, sugar and salt in large roasting pan. Place chicken skin side down in water mixture. Add more water to cover chicken if necessary. Cover and refrigerate at least 12 hours or overnight. Preheat oven to 300°F. Drain chicken; pat dry. Place chicken halves skin side down in single layer on heavy large baking sheet with rim. Brush each chicken half on 1 side with 2 tablespoons barbecue sauce. Sprinkle each with 1 1/2 teaspoons rub. Turn chicken halves over. Brush each half with 2 tablespoons barbecue sauce, then sprinkle each with 1 1/2 teaspoons rub. Bake chicken skin side up until meat thermometer inserted into thickest part of thigh registers 185° and chicken is deep mahogany color, basting every 20 minutes with pan juices, about 2 hours 15 minutes.