Preheat grill on high.

Pat the chicken thighs dry with a clean paper towel. (discard the towel immediately) Season with salt and pepper on both sides. 

Place the chicken on the grill skin side down and cook for 4-5 minutes. If the fat rendering off the chicken causes flare ups, turn the heat to low. When the skin is crisp, flip the chicken over and continue cooking for an additional 4-5 minutes. 

Baste the chicken with barbecue sauce on all sides, turn the heat to low if you haven't done so already and close the lid.  Continue grilling the chicken for an additional 4-5 minutes on each side. Test the chicken for doneness with an instant read thermometer. (thigh meat should read 185-205 degrees F)

Baste the chicken again and cook for an additional 1-2 minutes.

Transfer the chicken to a platter and rest for 5 minutes.

Serve with additional sauce on the side and sprinkle with cilantro if desired.