When I do wings with my vortex, I usually don't put anything under them since they are around the outer area of the grill. It would be kind of tricky to foil that area. When I am done with the wings, I pull the vortex out, move the coals to the outer area and let the coals burn the grease off. Same technique should be applicable to other indirect cooking methods, just move you coals to the indirect side once you are done cooking at let them burn off the drippings.