1990 80 G54 rear emergency brake mechanism

[Al]

Hi guys/gals,
I have noticed that one of my rotors on the rear is not shiny, at least not a shiny as the other side. I use the parking/emerg handle when I park the car. I lay behind the rear wheels and watched the parking brake being activated. One moved a lot the other very little and when released the good one opened or unclamped quickly, not the other. 
I have looked in the Bentley but nothing about that section of the caliper. 
Is there a way to grease or lube the pin that goes into that parking brake assy?  Is there a bearing involved?

Any BTDT or directions to a manual?

Regards,
Al