Some of the WL finders are assembled using shafts that run the length of whatever flap is being moved.
They pop up because there's a spring on the shaft pushing outward.
Needle nose pliers work as well as using a piece of wire to simply push the shaft out. because of the sizes involved I'd use the pliers.

Rangefinder forum has several threads on dechroming camera parts, It seems like the method most recommended is an acid bath with an electrode and anode with a metal piece to receive the chrome attached to one of them. I really don't remember the details