My son has been using a “Type To Learn” program at his school aimed at teaching the kids the right way to type. Perhaps that might help the people you are coaching as well. He had it for almost 8 weeks at about an hour each and as I understand it (I only hear from him and have not tried it myself), he is taught a couple of letters at a time and eventually get quizzed on it (somehow) and then can move to the next level. If he fails the quiz, he redoes that “level”.

I, personally, learnt on an old fashioned typewriter in India, so the skill itself is less a computer skill and am sure has it’s equivalents in Indian setups. Of course, the MS keyboard helped force the finger positions especially for the center keys.