Yes, Garry is my Sifu.
YKM would always have air in reserve. The breath is never let all the way out. We breath out through the nose with short breaths for each strike and breath in when we step or when clawing inwards. I have a feeling that the shock from the Dan Tian can be produced both ways - breath out or breath in. The ging expands out in all directions (with the use of fau chun tun tau) - down the legs and up out the hands.Air is pressed into the dan tien. Then the energy wants to come out. The main path out is through your arm. On the other hand power is used downward and backward through the legs. Thus the balance of power is generated.
We also sink in out stances when we pull in as well as sinking on some stikes.
Hope that helps.
Lowlynobody.