Beef Broth: This is something I've been adding with the enchilada sauce I tend to purchase to keep in my pantry for shortcuts. I use the Sprouts store brand Organic Enchilada sauce, and it tends to be thicker, and when used on its own it gets too thick when slow simmered. Adding a small amount of broth gives me the perfect consistency. You may want to try this trick also to get a nice smooth sauce when slow simmering the meatballs.