I think it's just a question of experience. I haven't ever seen about special education for this kind of work. If you work with restoration of docs, you must have definite skills, but they are given during courses and education before the start of working there (I think so). They have very low salaries there. Very low! Like many budget workers, so I think they are glad to have any workers, and they are ready to teach them by themselves. It requires lots of attention and carefullness, but I think it's possible to get necessary skills rather fast.