If you plan ahead, lay the wings on a rimmed baking sheet and let them dry uncovered in the fridge overnight. Alternatively, pat them dry with paper towels.
Preheat the oven to 250 degrees F. Put one shelf in th the lower quarter of the oven, and one in the top quarter.
Line the baking sheet with foil. Spray the rack on the baking tray with oil.
Place the wings in a large bowl. Sprinkle over baking powder and salt. Use hands to toss well to coat wings evenly.
Place the wings skin side up on the rack (ok if snug, they shrink). Bake on the lower shelf of the oven for 30 minutes.
Move tray up to the higher shelf and turn the oven up to 425 degrees F. Bake for a further 40-50 minutes, rotating the tray halfway through. The wings do not need to be turned over.
The wings are ready when they are a dark golden brown and the skin is very crispy.
Toss with buffalo sauce, and serve immediately with ranch dip and celery sticks. Use the extra buffalo sauce for dipping. Wings also reheat crispy!