I have to admit that I don´t really understand exactly how some of the shortcuts work.
For example, with Shen you can make qcf+P and leave K press to cancel geki-hen into tenrenken and viceversa.
But in some situations it just doesnt work, it thought it was a more consistent thing, but it is not, in some situations you just have to do it manually.
An example I found of this is the following:
HD mode: qcf+D (tenrenken) press A (geki), qcf+D (tenren) and the opponent goes into the air and now, 2 things can happen:
-if you make qcf+D and hit him really low, you press A and you get the geki and then repeat qcf+D
-if you make qcf+D and hit him higher, and press A the geki won´t come out.
In that situation there is not diferent in the attacks, the only difference is if you hit the opponent closer to the ground, but that shouldnt affect the shourtcut, regular tenrenken is a 1 hit attack and if it hits the cancel should come out right away, the geki would probably miss, but that is not the point. The point is there seem to be little things that make the shortcut "available" or not.