Hours are largely irrelevant ...
.... train to competency.
Some will "get it" quite quickly, some will after period of time, some never will.
It is impossible to set an exact number of hours on how long this process will take.
I would add that "safety" is a continuum, not a binary concept.
Last edited by oleary; 24th October 2016 at 19:56.
Reason: Add safety comment.