South carolina slow cooker pulled pork

For the sauce:
Combine the cider vinegar, ketchup, brown sugar, salt and red pepper into a mixing bowl. Stir until the sugar and salt have dissolved. Cover and refrigerate. (Decrease ketchup and brown sugar for increased tartness.)

For the pork:
Combine the onion salt through the pepper and add an 1/8 cup of the brown sugar in a small mixing bowl. Reserve 1 tablespoon of the spices for the next day. Rub the remaining seasoning over the pork ribs, covering all sides. Wrap the pork in plastic wrap and refrigerate overnight.
The next morning, heat the olive oil in a large skillet. Add the pork and brown it on all sides, about 8 minutes. Transfer the pork to the slow cooker. Next add the reserved tablespoon of spices, the cider vinegar and the remaining 1/8 c brown sugar to the skillet. Heat the mixture while dislodging any browned bits from the pan. Once boiling add the liquid to the slow cooker with the pork.
Place the cover on the slow cooker and set the temperature to low. Cook the pork for 5 to 8 hours, until fork tender. To serve, remove the pork from the slow cooker and cut into one-inch thick slices, then shred it with a fork and knife. Return the pork to the slow cooker and stir into the warm sauce. Serve warm over soft buns with South Carolina BBQ sauce on the side for dipping.