Being too much of a maniac with such thing is no good. Especially not for your kids: an environment that is too clean will prevent them from developing proper defenses and as soon as they'll be outside, they'll get sick like sissies all the time :-/
That's why I prefaced with "If your goal is to get clean." Sometimes it's just to satisfy a taboo. That's okay.
http://women.webmd.com/home-health-and-safety-9/places-germs...
If you want to avoid your kids getting sick, I can recommend getting them a flu vaccine. Probably safer than relying on a faucet containing the exact amount of virus you need to develop antibodies.
Citation needed.
I've never met the "do not touch anything dirty after you washed your hands" and "close the faucet with a paper towel" (!) as a recommendation against spreading flu virus.
Especially if by "dirty thing" you mean the faucet handle.
Back a while ago I worked to pay for college. One of the several jobs I held was as CNA (Certified Nursing Assistant). Before they let you do the job there was a class you had to complete and one of the skills that you got tested on was washing your hands. Because, the first thing you did upon entering a room was to wash your hands and the last thing you did before leaving it was to wash your hands.
The process was as follows: set paper towel dispenser with 8-8 inches of paper towel so it is ready. turn on water to very hot. Wet hands and apply soap. Work soap into a lather for at least a minute and pay attention to make sure all surface areas of the hands and wrists are thoroughly scrubbed. Rinse under the hot water and tear off the paper towel. Use the paper towel to grab and dispense more paper towels for drying the hands. Once hands are dry, use the paper towels to turn off the faucet.
The keys to washing hands well seem to be related to water temperature and the length and vigorousness that is applied to the scrubbing. Once hands are in a 'clean' state the key to keeping them clean is to avoid contact with anything 'dirty'. I don't have a citation but if you really want something related to the measured effectiveness of hand washing techniques I am sure I could find some studies on pub med if you need them.
Depends on the ailment, Einstein. If its virus doesn't survive outside the body (which a lot of them do not), then "reducing the touching of things" does nothing.
And if the chances of catching it from a faucet are minuscule compared to someone having it breathing in the same room as you, then again, "reducing the touching of things" (especially when you already washed your hands) will gain you very little.
Ever heard of profiling and diminishing returns?
(danish, pdf) http://www.ssi.dk/Smitteberedskab/Infektionshygiejne/Hent%20...
Edit: That one is not specifically for flu, but too avoid infectious diarrhoea. We had a similar one at my job, specifically targeted against viral infections.