When I do it, I use what is called an aircraft drill bit. It's ~18" long, and small (I use 3/16" bit).
After routing for the pickups and the control cavity, I drill from the neck pocket all the way down to the bridge, and then I drill from the bridge pickup route into the control cavity. That way there is a hole running from the neck pickup cavity into the bridge pickup cavity, and then the bridge pickup cavity is connected both to the control cavity, and to the location of the bridge, for the purpose of grounding the bridge
Make sense? It's almost 1:00am here, so I'm not *entirely* sure how much sense I'm making, but it makes sense to *me*...
