I brought mine back to life by bathing it in a few long soaks of 'white gas' as we in north america use in portable camp stoves. Fresh solvent for each soak. Cover the dish between times you attend to the shutter to keep the solvent from evaporating away.

After two soaks I was able to remove the retainer for the rear lens element. I used snap ring pliers to manipulate the rear retainer ring off.
Take care to note the correct orientation of this element on removal, and if there are any spacers used as well.

Then after a few more soaks, I would shake the most liquid out as I could, and proceeded to blow dry the thing to speed evaporation.
Ever so gently adjust the aperture to dry those leaves out.

Then start with B, and excersise the shutter to get the shutter leaves dry.
Sometimes a very gentle touch with a dry q-tip can spread the remaining solvent while the shutter is closed to speed the drying.

Then I used the same solvent to get the mirror pivots and helical adjuster in the uncoupled rangefinder to move.

The next fight was with pin holes in the corners of the plastic bellows. I found a light smearing of RTV black gasket silicone worked best.

Good luck.