SO I have been playing around with what is conductive.  Sand is not.  Sand from the sandblaster, coated in the worn off metal shavings is not.  Coal dust is not.  This afternoon I will go over to the hard ware store to get some graphite powder.  It is too fine to use on its own, but maybe if I mix it with the sand it will work.

Is salt conductive?

I have also been thinking that maybe the medium dosent have to be conductive.  If I have a variety of prong sensors sticking up through the sand, not visible mind you, but enouhg to periodically brush the rake that would be enough.  I'll see this afternoon whether I can get anything to read current, if not I think that is the path I will take.