Well first off I think you make the wrong assumption that a defensive swing is primarily in an effort to try to get a foul ball. A defensive swing is done in an effort to make contact, no matter how slight, because the pitch is too close to the K zone to let it go, with the hope that it will be put in play to or through a hole. I'm also assuming you're not talking about a check swing which I assume you now how to do. I think that about the only thing close to a defensive swing would be to not move the location (left) stick too erratically in any direction or even at all. In fact, depending on what you're trying to accomplish, possibly moving it slightly horizontally left or right might bring that effect, as might up or down.