Another facet of cockpit hygene is, of course, the tendency of some pilots to transfer their proboscidiferous excrescences from soggy, germ infested tissues to the power levers, thrust taps or whatever, thereby contributing significantly to the morbific spread of coughs and sneezes, especially in the winter season.
For this reason, I advocate a cockpit policy of one Kleenex, one blow and a liberal application of Dettol Disinfectant Spray to all surfaces which might be contaminated or subject to deturpation.
Perhaps, quite apart from twiddling the knobs, that's another reason to sport those sensual off-white kid gloves so beloved of those who suffer from perspirative palms.