Mike Sigman has a new blog, check it out.
His basic theory is quite good. When you read it note that "san waihe" (three external harmonies) is a description of the way the body should be organized not how it should move or be motivated. The external body he describes needs to be empty (xu) of intent and effort. The movement of the external body can then become unconscious.
The internal body (what he calls "san neihe" and will hopefully deal with in future posts) needs to do a different job than the external body. As I have said many times, the internal body is moved by changes of the spatial mind. The external body must be completely within the spatial mind and unconscious, any spatial mind inside the body will break the system. If the internal body does the same movement as the external body it is still possible to have some internal strength, but it is so much cooler if the internal body goes a different direction and moves in a totally different way. The internal body should attack the opponent directly, not through the external body, not through the limbs.
He embedded this video of Chen Bing doing simple stuff.
At around 3 minutes he uses the term "tong bu" which is translated as "synchronized." There is another tong 通 (first tone instead of second tone) which refers to emptiness passing through the gates. I don't think he is making a translation error here, I just don't think "synchronized" is helpful because the dantain is not doing the same job in the same direction, it's doing something quite different. Tong 通 is implied in his statement that the hand must remain "alive" (ling). When you have the feeling that the hand is inside the dantian it is much easier to keep the gates (at the shoulders) open.
I know all this stuff I just said is probably hard to follow, perhaps impossible. That's why I appreciate Mike's blog post, it is fairly easy to follow, it is a clear beginning. He suggests that forms should come later, after learning these basics and he has a good argument to back it up. That's not traditional but it might work better.
The other thing I like is how clear he is about the central importance of up/down power. He calls it gravity and power from the ground. Most people, most trained martial artists, can not fully use up/down power because they are in a trance. They try to replace gravity with strength & control thereby losing whole body mass, they end up carrying themselves instead of making their opponent carry them. They also loose upward power by arcing it forward through their limbs as vectors into their opponent. Ahhh, in praise of simple up and down.