Preheat a large ovenproof pot to medium-high heat with a drizzle of oil. Preheat the oven to 275F. Sear the short ribs on all sides, for 10 or so minutes, sprinkling on 1 teaspoon each of cumin, chili powder, and seasoning salt as you go. When the ribs are dark and crusty on the outside, remove them to a plate to rest.
Reduce the heat on the pot to medium and add the beer. Deglaze the pan, stirring to remove any bits from the bottom of the pan. Add the garlic and remaining cumin and chili powder, then add the worcestershire sauce. When the beer has reduced by about half, add the short ribs back to the pot. Pour in just enough stock to nearly cover the short ribs.
Cover the pot, and braise in the oven for 4 - 6 hours until the short ribs are fork tender. Shred with forks, discard any connective tissue and the bones, and serve in soft tacos as desired.