Please clarify what you meant by "pushing off"

If you've not already done so, you might do well to grab a copy of the book The Stack and Tilt Swing by Plummer and Bennett. Aside from being an excellent supplemental reference guide for the online school, it does go into some detail on moves such as this.

I'll consider doing a lesson on the upward thrust of the lower body, but I've been hesitant to do so for a couple of reasons:

1) The motions you are learning by working sequentially through the course curriculum and mastering the drills will ultimately lead to the upward thrust occurring naturally and without conscious effort.

2) If one were to actively focus on the upward thrust - or "jump" - move, then there's more than a fair chance that it will throw the downswing sequence out of whack. (And by the way, do not equate this "jump" to the Justin Thomas/Lexi Thompson version where both feet are pretty much off the ground. For example, have a look at Mike Bennett's driver swing. And here is one of Charlie Wi that I just found where Peter Kostis put him on the Konica Minolta Swing Vision and talks about the upward thrust. It's certainly more aggressive than Bennett's move, but still there's no jumping off the ground.)

For now in this regard, I recommend just trying to get a feel for the ground force that you are creating as you remain centered while gradually increasing the forward weight load throughout the swing motion. Beyond that, get the book!