So, I've done several killswitches on my guitars. Logically, at first, I thought to wire the switch so that the signal goes through the switch, then when you flip it, it opens, and disconnects the lead from the pickup from the output jack. That turns out to be pretty sucky, because it basically turns your guitar and guitar cable into a giant antenna
Alternatively, if you wire the switch with a tap from the hot connection (basically the TIP of the cable) and the other side to the ground, then when you close the switch, all the signal just dumps to ground, and you have a completely silent guitar, no matter how much gain is behind it.
So then, a DPDT will have basically two sets of these lugs, so one side can disconnect your battery power (interrupt it), and the other can then connect the hot to ground.