Volunteers?...........................meaning I do not get paid?
Well, OK. I will do it for the good of the community. First you have to sign a waiver stating that you will not sue me if you get squirted in the eye. You know how it is with grapefruit.
The pH of grapefruit is low, ie. acidic, and you don't really want this to go into your urethra by accident. If it does, you will probably scream and jump, but not "with joy"....lol.