A friend of ours is an Assistant Chief in a local fire department; formerly, she was a nurse. She suspected the firefighters of not washing their hands after using the facilities. To drive home the issue of spreading germs, unbeknownst to them, she placed a chemical that reacts to ultraviolet light on the inside of the mensroom stalls. IF, they washed their hands after exiting the stalls, the chemical would wash off. If not, the chemical would be transferred to everything these guys touched.
Later that day, she held a training class to review the subject matter. She asked how many regularly washed their hands after using the bathroom. Of course, all hands went up. Then, she brought out the ultraviolet light. It was gross. All these guys had stripes of the chemical on down their pant legs, on their shirts, on their faces, by their eyes. Then, they walked the station; this stuff was EVERYWHERE. On all the doors, even the refrigerator, on papers.
They were very embarrassed, and it certainly drove home the point!
Justitia