Your question on ji led me back to an old thread http://www.yangfamilytaiji.com/ubb/Forum1/HTML/000018.html
where some discussion of press energy came up, including some occurrences in the form, such as the transitions from Lift Hands to White Crane Displays Wings and from Needle at Sea Bottom to Fan Through the Back.
I also posted a translation of a couple points on ji from Yang Zhenji’s book, _Yang Chengfu Shi Taijiquan_, p. 30:
2. The ji method is the employment of closing jin and long jin. Closing jin (hejin) is the two hands joining together producing one jin and applied on the opponent’s body. Long energy (changjin) is the entire body from the feet to the legs, then the waist, expressed in the hands and arms, and strung together into one jin, extending the waist and lengthening forth to issue.
3. A direct line of fajin. The method of ji is one of issuing force in a direct line. In Yang style taijiquan, when one issues, one “seeks the straight in the curved” with specific regard to the focal point of the opponent’s center line, seizing the opportunity and strategic advantage (dejideshi), and issuing jin along a straight line (zhixian fajin) rather than in a curved arc.