Hi

The first problem with a Barnack i.e. a IIIg or earlier is you need to trim the film to the old leader standard, i.e. carry a small pair of scissors.
Loading properly trimmed film is then easy unless you have two left hands ( I apologise for that as well.)
They are like M2s you need to count the blank frames and set the counter manually.
They only take screw lenses and the Elmar aperture adjustment is difficult.
Best plan is buy a CV /2.5 5cm, if you are taking photos as opposed to stroking Leica gear.
Setting the shutter speed requires a lift the dial and drop in place and is only at the datum point if the shutter is wound.
Lastly if you snag the speed dial as the shutter fires the negative will be useless.

Noel