What about bandaids? How long did it take to learn?
Good question. I learned on a straight razor close to 40 years ago, but switched when I went to college. It just wasn't practical in the dorm. So, I kind of knew what I was doing when I switched back, but it still took about a couple months (maybe less) to get to the point where I wasn't cutting my face once a week.
As long as your blade is very sharp, you get to the point where you virtually never cut your face.