We began wiring the CP last night, specifically daisy-chaining the ground wires. It was much of the same process, but we got it down to an assembly line sort of, and it really didn't take that long. Cut wire to length, strip both ends, stick into quick connect, crimp. Repeat 54 times. (Pro Tip: get GOOD wire strippers, it will make your life easier).
Half of the CP is daisy-chained together and goes into one ground on the interface. The other half? You guessed it.
All buttons and joysticks are grounded.