Pour a couple tablespoons of the bar-b-q sauce into the bottom of the slow cooker. Place the chicken on top, then pour the remaining sauce over the chicken. Cover and cook on low for about 4 hours.
Once the chicken is done, remove from the slow cooker. Allow to cool enough to handle, then shred. Return the meat to the slow cooker and mix with the juices. Preheat the oven to 350°F and lightly spray a baking dish with nonstick cooking spray. Slice the entire loaf of rolls in half horizontally. Place the bottom half in the baking dish then place the shredded chicken on top. Then add the top half of the rolls.
Make the sauce by combining the melted butter, bar-b-q spice rub, Worcestershire, sugar, and mustard in a small bowl. Pour the sauce over the sandwiches. Bake immediately or allow to marinate for no more than 24 hours (covered in the fridge). Bake uncovered for 15 to 20 minutes or until the tops of the rolls are a deep golden brown.
While the sandwiches bake, make the slaw by combining the slaw mix and pickles in a large bowl. Make the dressing by combining the mayo, pickle juice, sugar, salt, and garlic powder in a small bowl. Pour it over the slaw, mix well, and refrigerate.