Pat the chicken thighs dry with paper towels. Score the underside (lengthwise) of each thigh with a few shallow slits to help the rub penetrate.
In a small bowl, combine the homemade dry rub and liquid smoke. Rub the mixture all over the chicken thighs, coating them evenly.
Preheat the grill to a medium-low direct heat of about 300°F (150°C).
Place the thighs skin-side down over direct heat and grill about 2 minutes, then turn and grill about 2 minutes on the other side; repeat as needed, turning a couple of times to avoid burning and brushing with olive oil while grilling.
Move the thighs to the cooler side of the grill (indirect heat), cover, and continue cooking for about 6–8 minutes, letting the hot air finish cooking the chicken while retaining juices.
Continue grilling until the internal temperature reaches 165°F (75°C). Remove from the grill and let rest briefly before serving.