Hi again, WSW,
I did experiment with the 9 volt battery. I used a light tapping with a wet finger. I wet a paper towel and took a piece of it and placed it over the negative terminal. When the fingers are wet you can feel a slight tingling in the finger that you have over the negative terminal as well as the finger you are tapping with on the positive terminal.
Look up some of Jessesmom's posts as she has some information as to how this worked for her, too. Just click on "Jessesmom" on one of her posts on the icon on the top right, the pages will come up of all her posts. This way you can find the ones she has written about the zapper.