For bears, the advice we got from Fish and Wildlife was to bait the fence with aluminum foil smeared with bacon grease. That gets the bear to touch it with their sensitive nose. If they brush up against it with their thick fur, they won't notice. A good zap on the nose will teach them.

I can confirm your note about footwear mattering. I'm way too cheap (read: stupid) to buy an electric fence tester, so I just touch the fence. In dry shoes, it's noticeable. The one time I did it in wet sneakers, it definitely got my attention. For what it's worth, we have about the smallest fencer Tractor Supply sells (it just has to go around the chicken coop). I betcha a 50 mile fencer would just about make your hair stand up on end.