While there is no harm in keep oils from your hand off of the tube, it is hardly necessary. The tubes do not suffer from the same failure mode as halogen, metal halide, etc. bulbs.
When oils from your hand get on the bulb, the high temperature carbonizes the oils and this forms a dark spot on the bulb. That dark spot will then absorb light from the bulb, instead of passing the light through, which heats that particular spot more than the rest of the bulb. That temperature differential causes the bulb to explode. Your tubes never get hot enough, nor do they put out the huge amounts of energy that could cause that kind of hot spotting from what is on the glass.