I would be careful coating the circuit board with a conformal coating of this nature for fear of changing the heat dissipation capabilities of some of the electronics parts on them. You might find overheating becoming a problem.
Steve what you are doing is a lot of work and it makes the forum a heck of lot easier to navigate. Thanks for such a nice place to spend our time and the excellent job that you do keeping it up. It's a gem.
http://www.onelight.com/hec/targets/Alaska/Stan Grist's resources for treasure hunting, gold prospecting, metal detecting and exploration. .htm
This guy I think