This sounds really good. I think I would cut down on the hot sauce because a whole bottle seems a little much.

Slow Cooker Mexican Style Meat
1 (4 pound) chuck roast
1 teaspoon salt
1 teaspoon ground black pepper
2 tablespoons olive oil
1 large onion, chopped
1 1/4 cups diced green chile pepper
1 teaspoon chili powder
1 teaspoon ground cayenne pepper (or to taste)
1 (5 ounce) bottle hot pepper sauce (or to taste)
1 teaspoon garlic powder
3/4 - 1 teaspoon cumin

Trim the roast of any excess fat, and season with salt and pepper. Heat olive oil in a large skillet over medium-high heat. Place the beef in the hot skillet, and brown it quickly on all sides. (or brown it after it is cooked and shredded)
Transfer the roast to a slow cooker and top it with the chopped onion. Season with chile peppers, chili powder, cayenne pepper, hot pepper sauce, and garlic powder. Add enough water to cover 1/3 of the roast.
Cover, and cook on High for 6 hours, checking to make sure there is always at least a small amount of liquid in the bottom of the cooker. Reduce heat to Low, and continue cooking for 2 to 4 hours, or until meat is totally tender and falls apart.
Transfer the roast to a bowl and shred it using two forks (reserve 2 cups of cooking liquid, if desired). Serve in tacos or burritos.

If using the meat for burritos: shred the meat and add it to a frying pan with 1 cup of the cooking liquid. Simmer until the sauce has thickened, about 15 minutes.
To freeze the meat, transfer it to a freezer-proof container and add reserved 2 cups of cooking liquid. Freeze up to 6 months; thaw in refrigerator or microwave.
This recipe also works for pork and chicken. If you're using chicken, remove the skin before cooking and reduce the cooking time to 4 hours on High or 8 hours on Low. Remove the bones and shred the meat after cooking.

Chimichangas:
Spread flour tortillas with sour cream and put some of the meat in the middle. Fold the sides in, roll up, and fold the ends like a burrito. Place on a cookie sheet and brush with butter or oil. Bake in a hot oven until crisp on the outside. (This is instead of deep frying them.) Serve with finely shredded lettuce, diced tomato, and finely minced onion. You can also smother them with a fine green chili.