Bar was right on the money for me. The sense of connection of the palm of the hand to the sole of the foot powering it, with the dan tien magnifying it - that's what I'm working with at the moment. There is the obvious path of the rear leg to the lead hand, and then the less obvious path of the front foot to the other hand. Then it all gets silly as I'm working on changing the connections mid flow, which feels like a process of refinement.
I take what I get from that to the heavy bag and focus mitts and try to work with it. Without the bag training I wouldn't be able to hit at all. Without the form training I wouldnt be able to hit anything like as hard unless I spent an awful lot of time just doing bag work. The form trains a bunch of other stuff so I feel it's more efficient.
I agree with John - posture testing shows people very quickly if they have the connections right. Walk in front of someone's brush knee - if they dont move you without adjusting what they're doing, then they haven't got it right. My teacher used to sneak up on me when I was training and get in the way/lean on me/push me, so I got used to being balanced in all directions and being able to move him without knowing he was there. It certainly improved my intent