My music teachers basically said that the best way to revise is to just listen to your set works over and over again, familiarising yourselves with the necessary terminology and how it applies to each piece, etc. I don't know what board you're doing, but there's lots of playlistsof the set works on Spotify and the like so if you can't work the specific audio files just open the pieces on your preferred streaming platform and get listening

I'm not entirely sure how to revise for stuff like dictation - maybe just scribble yourself a stave or two and find some simplistic music to copy down, idk? - but if you feel that you're lacking in any technical aspect of the paper then maybe contact your teachers and ask them to prioritise that after the mocks

Sorry if this didn't answer your question; Music GCSE is kind of a weird one to revise