How can the weak defeat the strong?"
Shen Fa - body method or body work.
This is the way that you coordinate the body to move the limbs.
So, if shifu says that your body method needs work, he would mean that the hands are moving devoid of coordination to the waist and torso.
1) 'Foot work' this would be bu fu, which is better translated as stepping method. How you dodge, leap and turn.
This article of mine describes it in more detail. The interesting thing of this article are the quotes from Qing Dynasty manuscripts of kung fu.
http://www.plumflowermantisboxing.co....htm#deceptiom