If you're thinking of doing the same thing with a wireless controller, beardawg252002 has done just that over at the Xbox-Scene forums.
The name, Gyokusho is actually stolen from a japanese chess variant called Shogi. The equivalent of the king is called the Gyokusho or "Jade general". The short hand for that is the sign you can see in the middle of the controller (see image below).
Oh, and by the way, it's huge.
Step 1: The disassembly
1 = A
2 = B
3 = X
4 = Y
5 = LB
6 = RB
7 = Back
8 = Start
9 = Left analogue stick click
10 = Right analogue stick click
Left analogue stick represents the analogue directions
X/Y axis are controlled by the right analogue stick and finally, the Z-axis is controlled by the left and right trigger. Right trigger increases X whereas the left one decreases it. Nice and simple.
I removed all the screws holding the 360 controller together, unplugged the vibration motors and presto, you've got yourself a nice and tidy circuit board. You don't have to use much force when doing this, if you can't get it open, you've probably overlooked the screw that sits under the sticker.
Removing the triggers takes a bit of effort but it can be done. Just make sure that the lever that's left is tied to the construction holding it (I just used some stripped wires and wound them around the plastic since superglue didn't do the trick). If you don't do this, the levers will move around and you'll probably get unwanted readings.