Air-drying duck is an old preservation method that also happens to produce something deeply flavorful. The trick here is using green Sichuan peppercorns (麻椒) rather than the more common red variety—they carry a sharper, more penetrating numbing quality. Crushing them before toasting coaxes out their essential oils, so the flavor really gets into the meat.
Any high-proof baijiu will do; I usually reach for Erguotou, but there's no need to be particular about the brand. In warm weather, keep the marinating legs in the fridge and give them a massage every few hours. After hanging outdoors to dry, stash them in the freezer. Before steaming, scrub the skin well with a brush—it's been out in the wind and weather, and you'll want to rinse off any dust.