Awnser: Too many damn variables. You're never going to get an exact awnser. It all depends on the people involved and the environment.
Imagine that one of the people you're trying to jerk off is paralyzed from the waist down and the room you're in is in the middle of a warzone in Syria. Not to mention you could also have very dry and rough hands.That is possible with this question. Just too many variables.
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