1. Combine sugar, paprika, garlic powder, onion powder, cumin, cayenne, and 1/2 teaspoon salt in bowl. Using fork, prick pork all over. Rub sugar mixture over pork, wrap tightly in plastic wrap, and refrigerate for 8 to 24 hours. Unwrap pork and place in slow cooker.
2. Spread barbecue sauce evenly over pork, cover, and cook until pork is tender, 9 to 11 hours on low or 5 to 7 hours on high.
3. Transfer pork to large bowl, let cool slightly, then shred into bite-size pieces discarding excess fat; cover to keep warm. Let braising liquid settle for 5 minutes, then remove fat from surface using large spoon. Season with salt, pepper, sugar, and vinegar to taste.
From America's Test Kitchen book: Slow Cooker Revolution.
4. Toss shredded pork with 1 cup braising liquid; add more liquid as needed to keep meat moist. Serve with barbecue sauce.