I was in the Washington D.C. area in 2003, attending a workshop by Grandmaster Chen Xiaowang. The highlight of the workshop, which focused on Laojia Yilu, was when we all got personal attention from Grandmaster Chen on fajing. I stood in front of him to do the hidden hand punch and when I sunk into my right kua before the punch, he said, "Too much." So I tried it again and he said, "Too much." I lightened up a little on the sinking and he smiled and said, "Ahh, okay."
Then he took both my arms in his hands, had me relax my body, and he jerked one hand forward and pushed the other in the opposite direction. He did that two or three times as if I was a puppet. The little lightbulb above my head went on. He backed away and told me to repeat it, in front of the entire workshop. I did, relaxing and letting the fajing fly. He smiled and said, "Okay."
In the same facility where we were training, a big kung fu tournament was being held the same weekend. On Saturday night, a masters demonstration was held. Here's the video of Chen Xiaowang's demonstration that night. This clip starts out slowly but then....WHAM!