Light a charcoal grill and lightly oil your grates.
Grill the pork shoulder and beef ribs on all sides until well browned.
Place a well oiled, large heavy Dutch oven over medium heat and add your meats.
Add your onion, garlic, oregano and cumin.
Pour in salsa.
Allow to simmer, partially covered. Stir often, until all meats are tender and falling apart. This should take about 2 to 2 1/2 hours.
Stir in cooked beans, beer and the dissolved masa.
Continue to simmer, stirring often - until slightly thickened. This should take an additional 10 minutes.
Serve with garnishes.