I can't recall if I saw this in the learning center on this site, or picked it up as advice from an instructor. It was about envisioning the tension or force from your body coming only from the front half of your body. This would be same for both partners, to help create the proper communication tension in the hands, arms and shoulders. When you think about it, this causes you to create tension without using too much of your back or shoulder blades. In other words, you are not pushing or lowering your arms, hands, etc. to make that push. It is a more subtle tension, flowing from the front half of your body. When you try to do it that way, you actually can feel your frame staying in place. When I am teaching someone, I will explain that phenomenon, but also demonstrate it by holding frame with a partner, and then asking the partner to indicate which way I am trying to guide her. She can answer because she can feel it, but those observing can't tell I've really delivered a specific signal, per se, because I am not "pushing" or lowering my arms to power a move. It takes some practice, and like the other posters noted on this topic, it is almost something you do without thinking about it much after you get the feel for it.
I believe it was on this site's learning center, and it showed motion arrows coming from the front half of the body.