The dot is the opponent's centre, the point that the opponent's doesn't want to move. Since he doesn't want to move, it can be used as the centre of the rotation that you want to do.
Direction of Power
Once you know the direction of the push of your opponent, align yourself such that the push through you goes to the ground. You can adjust your front side or your back side. If the opponent's power is less than yours, you can adjust the front side (e.g. your front hand), if the opponent's power is greater than yours, you adjust the back side (e.g. your back leg). You don't move the front hand when the opponent's power is greater than yours because you need to keep the peng. Putting the opponent's direction of his power on the line connected to the ground, is to bring his power to the ground.
Level of power and distance
We need to establish 5 points on the opponents. It is like establishing a perimeter for the opponent, so he can't get away. We start with 2, then 3, and so on.
All the points can't merge to the same point on the opponent. Each must has its own direction.
With 1 point having lots of power, it is very difficult to control. With 5 points, each has less power, and it is easier to control. We need to practice between 1 and 5 points, and eventually we can use them. (I don't understand this at this point, and I am just writing it down).
If the opponent only has 1 point on you, you move around it easily (NOTE: don't move the point itself).
To issue, bring all points back to the line (to one point).
Switching of Power
At first, we need to big actions (exaggerate our actions) to achieve the goal. In this case, it is to get under the opponent. Later, you can get under without physically going lower. You need to learn to control your body to achieve. The demonstration was that the student was bending quite low and Master Chen Zhonghua was standing taller than the first student, and his hands was top of the student, and yet he made the student feel that he was under the student. The next student pushed his belly, then his thigh, and finally his ankle, and yet he was always under the student.
Joke: 鹰抓趾功, A real eagle's claws are on its feet, Master Chen Zhonghua's are on the feet too while other people's Eagle Claw is with the hands. This joke came from the above point about how he was able to get under the opponent, like always holding on the ground.
Six sealing four closing: Master Chen Zhonghua demonstrated how he used his hands to hold/catch the opponent to cause him to tense up, and at that moment he turned his waist, and the arm would be broken. An arm couldn't fight the power from the waist.
Segmented moves avoid double heavy. Why? When we only move one part at a time, there is something else not moving. The two parts are not moving at the same time, and therefore, it is separated. Separation means no double heavy. It can be "moving hand and not moving waist", or "moving waist and not moving hand". By "moving", I mean to move from Point A to Point B.
That's why we perform our yilu in a robot fashion, in order to train the ability to move any of our body parts at will without affecting another part that shouldn't be affected in an involuntary way.