DD is Y13 now, but during Y10/11 she revised for specific topic tests by going through her notes and doing practice questions.
For exams/mocks she would do a mix of note taking, creating mind maps, creating fact sheets, doing online revision through eg seneca, quizlet etc, using CGP revision books and practice questions. Different techniques work better for different subjects.
She didn't do revision unless she had tests/exams because her school set a lot of homework.
I'm not sure how long she spent revising. Certainly in the Christmas holidays before mocks, she spent nearly every day working a full day, splitting the day into distinct sessions for different subjects.
Techniques not involving writing are fairly limited, and will be less successful for certain subjects. IF oyu are willing/able you can listen to your DC talk through answers to practice questions, get them to explain a certain topic/idea to you verbally, or test them on language vocab etc. Or they can watch videos on line or use interactive websites eg BBC bitesize, Seneca