In the case of the two Ukes holding the jo, we have to get them to push or pull so that they form a "unit". Then, no matter how outwardly casual we are, if we put our hands on the jo, we still must do it in such a way that the jo becomes part of our own unit. Become "one with the jo" and you automatically become one with the two centers of the Uke's. Now we're back to that basic skill of paths/lines/connections which you have to develop, but if you have that skill you can "feel" for the center of one Uke and then the other; sometimes both at the same time, but it depends on their positions. You have a good connection, you move their center with your center.
Does that help?
I didn't figure you were serious. But you never know
Anyway yes that gives me something to think about. As for nage I forgot the detail that nage was only using the tips of one or two fingers on the jo to connect to the two ukes. Whether they were pushing or puling I don't recall. And I can honestly say, at the time, I was probably unaware of what kind of attack I was supposed to be giving beyond just holding onto the jo and keeping it still. This was a year ago and I was just preparing to test for 6th kyu, attending my first full seminar.
Feeling for the center of uke I understand. It gets a little tricky when you want to hang onto uke number one while looking for and connecting to uke number two. I know what it feels like I just don't know how to explain what it feels like....