So, I've asked if you can transfer Pokemon from Guardian Signs, and my answers said yes. But how is that possible if you don't KEEP the Pokemon, just use them in the field.
You can not transfer just any Pokemon from Guardian signs. Like Shadows of Almia you can only transfer specific event Pokemon for Guardian signs. You download events from the Ranger net similar to the way you get event Pokemon from Mystery gift. Unfortunately I think you missed all the events for this game. All the events have already passed http://www.serebii.net/ranger3/wifi.shtml except the Giratina and Arceus events outside of Japan, but they may not even happen outside of Japan.