Soak chicken in buttermilk with garlic, onions, herbs, paprika, and cayenne pepper. Refrigerate overnight or at least 8 hours. Drain in colander, leaving some herbs on chicken. In a large paper grocery bag, mix flour with seasonings. Meanwhile, heat 3 cups shortening in cast iron pan until 350 degrees. Place chicken pieces in bag with flour and shake, let sit 1 minute, then shake again. Add chicken to hot pan and fry on 1 side for 20 minutes, then turn to finish.