An 8-pound shoulder easily feeds 10 to 12 adults plus a handful of small kids as a taco filling. For a smaller group, up a 4 to 6-pound shoulder instead, reducing the cook time a bit and halving the spice rub. Use a whole bottle of beer, regardless. Cook this dish completely ahead; cool, wrap tightly, and keep in the refrigerator, in the braising liquid, for up to 5 days, or in the freezer for up to 1 month. Reheat slowly in a large Dutch oven over low heat. (If frozen, bring to room temperature before warming.)