I didn't help with the actual revision generally, unless specifically asked to test her on things.
But I helped support her to make a good revision timetable. She chose to do it on a shared apple calendar, which she shared with me. She said it helped to keep her focused if she thought I would also know what she was supposed to be doing when. She then had a large desk top planner which she copied it in to, but added more specifics of what she was going to study in each subject that week.
We paid to go and see relevant shows - either the plays shown via the cinema (such as MacBeth) or at home, via streaming services or buying them, and by buying any revision guides/books, audio books of plays/novels that she was studying. Dd was doing English Lit and Drama so plenty there.
Access to various revision books/guides if required, especially for certain subjects.
Paid for a tutor for maths to increase her confidence. It worked for us.
Provided a quiet peaceful and pleasant place for her to revise, with whatever stationary, etc she would need such as flash cards, highlighters, etc.
Provided opportunities for time out for a complete break every so often.
And was just general there and available as much as we (me and dh) could be.
16y look like adults but they aren't yet actual adults yet. In my experience support is needed in different ways. Schools do some revision support but many no longer have time to show teens how to revise. What works for one person won't work for others, so it's showing them various ways and them deciding what works best for them at the time.