Retina I viewfinder cleaning

I was given a 'freebie' Type 143 by an ebay seller as a bonus (I had just bought two very nice Retina I cameras, a Type 126 and a Type143, from him). It is in distressed but serviceable condition. Shutter works well except that T/B can't be set. One of the two rivets holding the pressure plate has lost its head. Other than that...

The viewfinder was cloudy.

Advance knob unscrews in opposite direction of engraved arrow. On my camera the shutter release button is a piece of knitting needle held down by friction. [I hope to insert directions for lifting the proper button]. Remove screws 1 and 2, lift cover plate revealing screw 3. Clean the finder.