In a bowl mix all the dry rub spices and set aside
Rinse pork and pat dry with paper towels.
Rub the Dijon mustard all over the pork. Then rub the spice mixture over the pork until well coated. Place into a baking pan fat side up. Cover and let stand in refrigerator over night.
Place pork roast into a slow cooker add a 1/2 cup water and cook on low 8-10 hours. Shred the pork using two forks in the juice. With tongs remove from slow cooker and place into a pan.
Leave the extra juice in the slow cooker to moisten the pork later if needed. Toss with a little barbecue sauce. Place under broiler for 3-5 minutes to get some of that crispy bark goodness.
Serve on toasted buns