Button Soldering Jig

This simple model will comfortably hold a momentary switch/pushbutton while you solder wires to its terminals. I use a cheap spring clamp to hold it in place. The STL provided is for buttons with 12mm shafts, but you can easily generate different sizes by editing the parameters in the OpenSCAD file. 

The jig should hold your button securely enough for soldering purposes with just a friction fit, while allowing the freedom to rotate the button as needed.