In a small bowl stir together the salt, brown sugar onion powder, chili powder, cumin, pepper, smoked paprika and mustard powder together until combined, set aside.
Take out your pork and stab 6, 2-inch deep holes fairly evenly spaced through the meat. Push a clove of garlic into each hole until no longer visible.
Rub the entire surface of the meat with the spice mixture, using it all.
In a large Dutch oven, heat the olive oil until very hot. Sear all surfaces of the meat, even the sides, until browned. The entire process will probably take about 10-15 minutes. Pour the beer over the meat, cover and reduce heat to medium-low. Cook for about 3 hours, turning the meat over about every 30 minutes, until the meat is tender and falling apart.
Once the meat is tender remove from heat, use two forks to shred into pieces while still in the pot (or remove, shred and return to pot). Return to the pot to heat and allow to simmer for about 5 minutes. Remove the meat from the pot, add to a servings bowl.
If planning on store the meat, reserve ½ cup of the cooking liquid to add to the meat while storing.