Begin by preparing the spice rub: In a small bowl, combine the ground black pepper, cayenne pepper, chili powder, cumin, brown sugar, dried oregano, paprika, salt, and granulated sugar. Mix thoroughly to ensure an even distribution of the spices.

Generously massage the spice rub into the pork shoulder or butt, ensuring all surfaces are well-coated. Wrap the seasoned meat securely in a double layer of plastic wrap and refrigerate for a minimum of 3 hours. For an enhanced flavor, the pork can be left to marinate for up to 3 days in the refrigerator.

Once ready, remove the plastic wrap from the pork. Transfer the meat to the slow cooker and add the optional liquid smoke along with a ¼ cup of water to the cooker.

Set the slow cooker to low and cook for 8 to 10 hours, or until the meat is fork-tender and easily shredded.

After the cooking time has elapsed, carefully remove the pork from the slow cooker and place it on a cutting board. Discard the liquid from the slow cooker.

Shred the pork by pulling it apart with two forks or your fingers, discarding any excess fat. Return the shredded meat to the slow cooker.

Add the barbecue sauce to the pulled pork, stirring to coat the meat thoroughly. Allow the mixture to heat on low for an additional 30 to 60 minutes until it reaches the desired temperature.