The way to get a potential player is not by having a seminar, or a booth, both because those are just poor tools for the purpose, and because the target is unlikely to bother attending. The way to hook someone is by having them *play*. But, as I understand it, the game seats at GenCon are largely booked up well before the con begins. So, your potential players have little opportunity to pick it up spur of the moment.
Thus, the Con doesn't seem a god place to recruit anyone who wasn't already trying to get into the game.