As above, consistent hard work and use of active recall are the ways to go for both subjects as they are very memorisation dependent.
By OCR chemistry, I’m guessing you mean OCR chemistry A. In terms of resources, I recommend Davies A level chemistry (for walkthroughs of past exam papers), Allery Chemistry, MaChemGuy and Mr Murray-Green Chemistry Tutorials (to cover the content) and Physics and Maths Tutor (for notes, exam papers and questions).