I included the directions here for the pork in the slow cooker, but you can obviously use leftover pork or make the pork a day or two ahead!
Season the pork with the salt and pepper. Heat the oil over medium-high heat (my slow cooker does this, if yours doesn’t, do it in a dutch oven on the stovetop!) and add the pork, searing it on all sides. You want each side to be golden brown. Place the pork in the slow cooker and add the beer. Cook for 8 to 10 hours, or until the pork falls apart easily.
Preheat the oven to 375 degrees F.
To make the enchilada filling, add about 2 cups of shredded pork to a large bowl. Stir in the garlic, green chilis and half of the monterey jack and cheddar cheeses. Add 1/3 cup of the enchilada sauce. Stir to combine.
Add another 1/3 cup of the sauce to the bottom of a 9×13 inch baking dish. Add the pork filling to the center of each tortilla and roll them tightly, placing them next to each other in the dish. When finished, cover the tortillas with the remaining sauce and both cheeses Bake for 30 minutes, until the cheese is golden and melted on top.