Electric fencing on wooden posts without plastic insulators?

My understanding is that wood is normally considered a poor conductor of electrical current, but this diminishes when the post is soaked.  There are apparently other factors that affect conductivity, too (see below).

Has anyone used electric fencing successfully with wooden fence posts (e.g. black locust) without using purchased plastic insulators?  

If so, what did you do or use or what would you do differently?

It will work to a point, but it's less reliable. Rain, dew, fog all create a grounding path. The output strength of the energizer becomes more important.

An alternative to plastic is the rubber from discarded inner tubes. Every bike store has a big bin of these out back. These are not UV stable so they only last a couple of years.

I used to have a length of fence on the property here where the battens were hardwood dipped (maybe pressure treated) in wax. They were sold for just this reason and held up for years with no audible shorting even after heavy rains. I don't think they'd be ground durable, but you could stable them to a locust post so that the wires are only in contact with the waxed timber.