Is the Rotisserie on a BBQ grill? Does it have a lid? You can kill one bird with one grill. Get a cast iron smoker box that goes gone the grill, and produces smoke. Soak some wood chips, and then wrap them in aluminum foil, and throw it on the grill. There are a number of ways to smoke on the grill. I would just do a reverse sear on the bird. Cook it in the smoker, and then stick it in a hot oven to crisp up the skin.