If the wall is heavily insulated, push conduit through the insulation and then feed.
How To Test A Wall Switch. You flip the switch up and down and can't quite figure out what it controls. Once you've confirmed that there's no electrical current in your switch you are ready to remove it.
How to Wire a 3 Way Dimmer Switch from ask-the-electrician.com
Testing a light switch electrical question: Learning how to wire a switched outlet is not difficult. Continuity testers are electronic devices with two electrodes attached to a digital meter.
Baley has published a series of books teaching how.