How long did it take you to become "proficient" with a hammer and chisel? (i.e. produce work you were proud of using just manual equipment with no air or spring assisted "helpers")
It might take a few weeks to get proficient with hammer & chisel. Maybe more, maybe less depending on your hand-eye coordination, etc. What will most likely be the biggest success/happiness factor is the artwork you're laying out.
I started my apprenticeship in August of 1979 & cut my first gun in October of that year.
I was working under the direct supervision of a Master engraver.... I doubt I would have made it that far that fast on my own.
I am not proficient at hand and chisel work. I personally use a Lindsay air graver. I would say that the time period needed to learn will depend on the individuals natural innate ability to learn new hand skills as well as the hours per day spent practising.