Here's a foolproof method to route those tiny slots for blade switches such as those on an S-Style or T-Style guitar. Requires a 1/2" guide bushing collar for your router (not included).
Router Guide Bushings 101: A guide bushing mounts to the router's sub-base with a tube that protrudes below. A straight router bit extends through the tube. The outer surface of the tube rides against an edge guide or template, keeping the bit a set distance (offset) from the edge guide or template. (Read the complete article "Understanding Guide Bushings" at Wood magazine)