After you finish learning the content, I'd advise going through past papers alongside the markscheme and make note of all the points on the markscheme for any question you can't get the answer to straight away. You're essentially making your own markscheme so that if you were to sit that exam right now, you have a sheet of paper which would have anything that could trip you up in the exam, eventually you have 20-30 of these that cover all longer questions, definitions, calculations etc. It's also making notes on only things that earn marks in the exam, so that helps too.
Just make sure to reword anything that might be different in the new spec, like in chemistry whether you use van der waals forces or london forces etc.