Lay the wings on a rack on a rimmed baking tray and let them dry in the fridge overnight. Alternatively, pat them dry with paper towels.Preheat the oven to 250F / 120C. Put one oven shelf in the lower quarter of the oven and one in the top quarter.Place the wings in a large ziplock bag. Add the baking powder and salt. Shake the bag to coat the wings evenly.Line the tray with foil. Spray the rack on the baking tray with oil. Place the wings skin side up on the rack. Bake on the lower shelf in the oven for 30 minutes.Then move the tray up to the higher shelf and turn the oven up to 425F / 220C. Bake for a further 40 to 50 minutes, rotating the tray halfway through. The wings do not need to be turned over. The wings are ready when they are dark golden brown and the skin is very crispy.Toss with Hot Sauce and serve immediately with Blue Cheese Dip and celery sticks. They can be served plain, with a dipping sauce or tossed in sauce.Whisk together the Sauce ingredients. Keep warm or reheat just prior to using.Mash the blue cheese with sour cream until smooth (or to your taste).Add remaining ingredients and mix well until combined.Store in the fridge until required. Remove from the fridge 15 minutes before serving.