Es

How to earth tuneomatic bridge

You earth one of the posts with a thin wire back to the control cavity. If you have untwisted bare flex in the hole before you put the post in you should get a perfectly adequate earth.

... and if the control cavity is too tricky, use the bridge pickup cavity, i.e. drill a small hole from that cavity to the (typically treble side) post hole.

Thanks for your help

Thanks for the reply