Coat a slow cooker with cooking spray. Combine first 8 ingredients and 1/4 tsp each, salt and black pepper.
Rub half the spice mixture all over the chicken breast and thighs.
Heat 2 tsp of the oil in large, heavy skillet over medium-high heat. Add chicken in batches and brown 3 to 4 minutes per side. Transfer to the slow cooker. Heat remaining 2 tsp oil in same skillet. Add onions and 1/8 tsp salt. Cook, stirring occasionally, until browned and soft, 7 to 8 minutes. Place on top of chicken, add the diced green chiles and the remaining spice mixture.
Whisk together the orange juice, tomato paste, lime juice, cider vinegar, garlic, hot sauce and 1/2 tsp black pepper. Pour over chicken and vegetables. Cover and cook until chicken is tender, 6 to 8 hours on low or on high for 4 hours.
Transfer chicken to cutting board and shred. Add sauce until chicken is just moistened. Serve with tortillas, avocados, cheese, cilantro, and additional sauce, if desired.