Rub the pork shoulder with a generous amount of the BBQ rub. I like to use one that has a smoke flavor to get more of that authentic smoked taste. Place the rubbed shoulder in the crock of a 5 to 6-quart slow cooker and pour 1 cup of chicken broth around the edges, being cautious not to wash the rub off. Cover and cook on low for 6 to 8 hours or until the meat shreds easily with a fork (about 190°F). Remove from the slow cooker. Once it is cool enough to handle, use two large forks to shred the meat.