Combine the buttermilk and hot sauce in a resealable container. Add the chicken pieces. If the chicken isn't completely covered, add more buttermilk. Cover and refrigerate 12 hours or overnight.
Fire up your grill with the Vortex BBQ in the center. Fill the Vortex completely with coals and let them light completely before adding the chicken.
Combine the flour and seasoning in a large baggie, bowl or pie plate.
Remove the chicken from the buttermilk mixture and shake off any excess. Add to the flour mixture and coat well.
Transfer chicken to the grill and close the lid with the vents wide open. Cook for 45 minutes or until the chicken reaches 165 F. You may turn the lid 90% every 15 minutes if desired, but I haven't found that it matters much on a smaller charcoal grill. On larger ones I do rotate the lid.
Lightly brush the chicken with some oil and cook another 2-3 minutes.
Remove and serve.