Is this something one can learn?
Of course! We all could focus manually “back then”, at least quite often!
What would you suggest?
Stationary models! (I have yet to nail a flying UFO; they are never sharp…)
Practice hyperfocal distance.
Small aperture (to get larger DOF).
For close-ups, use LordV’s advice: “Set lens to some distance. Sway, like when coming out from the pub; when object is sharp, expose.” (Link below.)
maybe only 1/10 of my photos will be in focus on a good day?
That is not a bad result!
Have fun!
Claes in Lund, Sweden