Rub chicken – Combine brown sugar, chili powder, paprika, pepper, dry mustard, onion powder, salt and cayenne in small bowl. Transfer half of dry rub to shallow dish; reserve. Pat chicken dry with paper towels and coat over and under skin with remaining rub. Transfer to plate and place in refrigerator, covered, for one hour.
Grill chicken – Grill chicken (skin side down) until skin is well browned and crisp (15-20 min)
Dredge chicken – Lightly coat skin side of chicken with reserved rub and return to grill, skin side up. Continue to grill, covered, for 15-20 min (until rub has melted into a glaze)
Rest – Transfer chicken to a plate, lightly tent with foil and let it rest for 5 minutes before serving.