I just get the nut down finger tight, and then hold it in place while turning the button using the prongs that hold the switch in place.
Once you get the nut down to finger tight you can tighten it the rest of the way.
If you want the prongs in a certain orientation, just keep loosening the nut a hair, and turning the whole button/nut combo until it tightens up where you want it to.
You want to be careful not to torque the prongs off the button though.
I can't imagine a button wrench getting them any tighter than I do using that method, and I can actually get the buttons close enough that they are touching each other on top using that method.