Different folks probably do it different ways. I always run ABC drill as very tight singles. I don't do the W.
edit: The purpose for running any drill (or marking set up) should dictate how you run it. I run the ABC drill primarily to get the dog comfortable running tight lines to gunners and old falls. Sometimes will have the gunner move after throwing (organized confusion) to get the dog to stay focussed on the mark with distraction. Singles are in order for these purposes.