I'm on the same boat and haven't revised for a single exam. I started yesterday.
I'm revising all the specification points. I do like 15 minutes on each specification point and also doing past exam papers.
WHEN YOU WRITE STUFF DOWN SAY IT LOUDLY IT HELPS YOU TO MEMORISE IT. Don't stress, I haven't done no revision but i'm never stressed hence why I got average grades on my mocks like 5s and 6s (WITH NO REVISION).
I just went on StudentRoom to take a break from revising done a hour or so and I ran into this post.
After you look at this comment, get off StudentRoom now. Follow this advice and stop asking for advice instead consume the advice. This is not directed at you, but most people doing GSCES usually ask for revision help and they don't really adapt. So, my tip would be get off StudentRoom and start revising THIS INSTANCE. I'm taking a break for another 10 minutes and i'm going to revise for a few hours.
Goodluck to you and everyone who sees this comment. I don't like competing with other students and I want everyone to get the best possible grades.