So here is an exploded view of you brake setup in the back.
Rear Brakes So there is a pin at the bottom of the shoe assembles that holds them on the metal standoff. That part is numbered 5.055. There is a pin lock on the backside, similar to part 5.057. It is like a washer with one side that is bent down and doesn't fit in the groove of the pin. You just bend it up and slide the pin lock off the pin. The pin can then be removed.
Here is an illustration of how the shoe assemblies are put together on the articulated links.
Shoe Assembly He has one of the pin locks in his fingers.
