In the Laojia Routine 1, Brush the Knees is a relatively simple move on the surface. However the shifting of weights between the legs and the sinking of the “gua”  are not obvious to many.  For beginners, they are usually taught to cup their hands somewhere near their left knee. Ask yourself, did you shift your weight when doing this ?
Whille we may like to grasp someone knee and destablises him/her, you may like to go for the waist and lift the person up.