So how does it work? He grabs your upper body and you 'bounce' him using the lower body and the ground. Wouldn't that say that there is a good connection between the lower body and the upper body? How do you see it?
Well first i will state that i am a student not a teacher and so still have a long road in front of me. Second i am not sure i can adequately illicit my ideas on paper (internet). So bare with me if it sounds inconsistent.
At the moment i think the idea is that if an opponent grabs my chest (say right side for argument's sake) then you relax the point of contact and the waist and send the force down to the opposite foot (left foot in this example). It also cause the chest to fractionally become concave, fractionally! Then by relaxing again via lifting the baihui point on the head and at the same time it relaxes the lower portion of the spine thus causing the force to come back up. This way a spiral of power is produced and it literally feels like you are doing nothing at all. As if the opponent is actually straightening you up for you and throwing/unbalancing himself. Well at least that is where i am at the moment. Like i said just a humble student.
You are probablly right with regard to not having the connection right yet, i freely admit that if i did then i would be able to do this at will unfortunately i can not!