Good technique to re-center proportioning valve?

[RedRider]

Problem: no brake fluid going to rear after installing a new CPP disc conversion kit. Front lines are fine.

Here is what CPP suggests:



The dash brake light is on so I assume the differential valve is stuck, shutting off flow to the rear lines. I closed the rear bleeders and opened a front bleeder while gently depressing the brakes...no luck with the CPP approach. Maybe I'm reading it wrong though.

Any suggestions on recentering the valve? I've read online of people using a small wire (or similar) to manually move the valve back to center.