In the tests I used sharp wire brushes to represent egg shells and diatomaceous earth barriers - both of which are often recommended.(The video demonstrates that they don't work).
The video also shows that my "brilliant" idea of having the slugs slime create a voltage when it connects between a copper and aluminum conductor didn't work either.
Slug pellets (chemicals) and beer traps have been used for years to kill slugs - trouble with those methods is that they attract slugs to the garden and the slugs munch away until they get to the "dessert".
The video demonstrates that the 9-volt electric fence is pretty well 100% effective.