I had a student for three years who had only one arm. He did everything.
When I anticipated that he may need assistance I simply sat next to him
and took cues from him about what he needed.
I did have a student last year who injured herself on a table saw (yes, it
did happen at school - not under my watch). She was back at school but in
considerable pain - hand injuries hurt a lot because they are so close to
the bone. she was pretty miserable. i put her on the computer and had
her scan all sorts of found objects and work with photoshop with them.
When she felt better she was back in business using both hands, even
though one was wrapped.