DIY Hybrid Mouse Controller Mods

[Ellipsis]

So when trying to use an xbox one controller for one hand and a mouse for the other I find that as all my digits are occupied as I have bumpers from modding it I can't really lift the right side of the mouse where I'm not holding it. This ends up being really uncomfortable.
Solution:
The playstation move navigation controller.
Problem:
I want to make buttons or bumpers on the back like the many xbox controllers that are out there so that I can have my left thumb on the joystick at all times. So That I will comfortably and FINALLY have the PC master race approved ultimate solution to have five functions on my left hand + ultimate omnidirectional, granular movement!
Solution:
Wire the traces of the buttons I want remapped to custom buttons drilled into the back of the controller where my free fingers will rest.
Problem:
I don't know what traces on the PCB are assigned to what buttons?!?
Does anyone know how I could discover such a thing?

 

[Ellipsis]

Tanks a million! Exactly what I was looking for!

 

[Ellipsis]

Primarily, open it up and find out! There will be contact pads where the plastic buttons meet the PCB (via rubber pads). You should be able to trace the tracks from there or simply solder some fine wire right onto those contacts. You might lose the main button functionality if you do the latter.

I will try that if all else fails.