I have not done Qi Gong/Chigung in my personal practice since focusing on the Yangs’ teaching. I did a moderate amount of it with other teachers who have had somewhat different approaches to Taijiquan. Each of these teachers seemed to have different reasons for teaching it. It certainly played different roles in their curriculums. I have not heard the Yangs focus on any of these particular reasons for Qi Gong and so have not tried to carry over this practice into their methods. Some of what I did previously I would even consider inconsistent with their approach; however, my impression of their views is that good Qi Gong is fine and bad Qi Gong should be avoided.
At present, I view Qi Gong as a practice that individuals may or may not benefit from, depending on their personal goals, the quality of teaching they have received, and what else they do in their practice. From what I have seen and heard, it seems that some people have very complex training systems, involving numerous forms, performed in different ways, and with numerous auxiliary exercises, such as Qi Gong, post standing (zhan zhuang), meditation, stretching, ruler exercises, ball exercises, etc. At the other extreme are those who simply concentrate on Grasp Sparrow’s Tail, freestyle Push Hands, and little else.
I think there are pros and cons to any type of training regimen, but that the best course is to find a good teacher, exhaust what he or she seems able to teach, and then perhaps look towards other practitioners whose level of skills you would like to emulate. As I have posted before, I am wary of being too quick to mix and match practices without having a thorough knowledge of the theory behind them and the role they are supposed to play in one’s practice.
I may have been exposed to something similar to what is described above as “shielding,” but various differences in terminology or approach make it hard for me to be sure.
What I have seen is a focus on the fact that Taiji techniques are not limited to particular combinations, that every part of the body should have Peng energy, and that every part of the body should be capable of striking. To demonstrate this, I have had one of my teachers use his torso to “push” me through my own pushing hand. He also once should me how he could neutralize my push against his body, trap my hand there, and then dance me around the room through control of my hand. This latter occasion was probably the closest I have come to being injured during Push Hands. Both techniques did involve subtle circling to neutralize my push, trap my energy, and then to emit energy.
These demonstrations were not presented as a separate type of technique, but rather as logical manifestations of other basic exercises I was studying. They were not presented as “shielding,” but I can see how these same “techniques” could be used that way if the practitioner had deep knowledge of energy and skill in manipulating it.