I got all 9s in science, and I pretty much did the same thing all the way through:
1. Identify the sub-topic that I understood least for the science I was revising. E.g. Electrolysis.
2. Use my revision guide to identify all key knowledge such as equations, properties, etc
3. write out the information in a different way.
4. Check and add anything I missed.
5. Go through an example question that has already been answered within the revison guide, ensure I understand everything that is ging on and why each step has been taken to get the answer.
6. Do a page of practice questions.
7. Mark practice questions HARSHLY.
8.1: If I got over 90%, I'd do another practice question a couple of hours later or the enxt day to ensure that i remembered it, but otherwise leave it.
8.2: If I got 70-90% I'd go over the specific things I got wrong and rewrite answers with the specification. I'd then do 1-2 other questions of the same type as the ones I got wrong.
8.3: If I got under 70%, it was back to the drawing board. I'd use the internet to do additional research, watch videos etc. To memorise difficult information, I'd use flashcards. Finally, I'd do some more questions and repeat step 8.
Edit:
I used this brand of revision guide/ revision workbook combo
https://www.amazon.co.uk/REVISE-EDEXCEL-GCSE-Combined-Science/dp/1292131586/ref=sr_1_1?keywords=edexcel+double+science+workbook&qid=1576345282&sr=8-1 but anything to your specification made by the exam board should be fine. Past papers are also great, but I saved those for easter when I needed to know what I desparately needed to go over.