I bought a 56/2 a while ago. Upon receiving it, I noticed the viewing windows were dirty and the shutter was a bit creaky.
Opening it up was really easy; there are just two screws on the long sides of the box. The rest of the camera is riveted in place and structurally cannot come apart any further. I blew some air to remove the dust and went at it with some general-purpose cleaner. The windows were cleaned with Windex. By setting the camera to T, triggering the shutter and blocking it with the small slide, you get access to the additional lenses inside. I used a minute amount of medium-viscosity grease at the spots indicated below to make the shutter slide a bit smoother. Additionally, I was able to add some grease in the take-up spindle as well by pushing the inner washer apart from the casing. Turns a lot smoother now.
Removing the upper metal contact, bending it back a bit and making an additional goose neck, I was able to synchronize the opening of the shutter with the closing of the circuit as seen below:
The contact is closed when the shutter is fully removed from the opening. The final note upon closing up the front: I first pushed one setting lever through the front and by using fine-tipped tweezers, I coaxed the other one (which is further back to give the levers tension against the front) through the opening.
I'll be taking it for a spin some time soon, and try out the flash as well. The windows look super bright now!