From Taijiquan: Through the Western Gate" by Rick Barrett
"The physical extension of a body part is preceded by its insubstantial correlate, called fang in Chinese. Fang is "reaching" with the mind, extending awareness before actually extending an arm or leg.
The substantial aspect of taiji power is derived from the body's tensegrity (song). It is easily triggered by pointing the index fingers and reaching (fang). Pointing and reaching establish the boundaries of the body's "tent". Relaxing into the structure that is formed keeps tense muscles from choking off the flow of qi."
I think that anyone who has been a U.S. participant in "push hands tournaments" is automatically suspect in terms of real Taiji knowledge. If you don't believe me, go look at any U.S. "taiji tournament" and watch. I've never met a U.S. tournament 'winner' who had even basic jin skills (this'll bring a few personal attacks) ... that's why I quit going to tournaments.
Here's a traditional admonishment about fangsong, but I'll say up front that like most traditional admonishments it does no good unless you already know what they're talking about; essentially it's about how to hold the body:
(Order: head to toe)1. Lightly close the chin toward the chest to relax the
2. Naturally open the jaw, place the tongue behind the front teeth at the upperpalate, and keep the lips closed (and relax facial muscles, especially the brow).
3. Relax the diaphragm (Hánxiong) to make the upper chest empty(
Shàngxû) and have a lightly rounded upper back (Bàbèi).Note. In general, "make the upper chest empty and the legs full (Shàngxû xiàshi) as a combination" and "relax the chest and have a rounded upper back (Hánxiongbábei)" are commonly used key sentences.
4. Relax the waist (Söngyäo) and keep straight line of the back and
5. Center the coccyx and sink it downward (Wëiluzhôngzhèng).
6. Fold and relax your hip joint (Songkuà).
7. Make the legs full (Xiàshi).
8. Maintain stability in both feet on the ground (Chéngën).
9. Inhale when raising the arms and exhale while hanging them in front of chest. Keep shoulders and elbows relaxed. (Chenjiänzhuizhöu)
10. Finally, breathe naturally (Zirànhûxï) and relax deeply (Song)