Either Kap.an or BPP is fine: you don’t need both.
The key strategy is lots of question practice using an exam kit (we also have some questions on our site). I also suggest that you use our notes and lectures for study and only refer to the BPP textbook as necessary.
When you do questions from the kit, don’t mark your choices there. Keep it clean so that you can retry questions without hints. If you get a question right, tick the question and don’t go back to it until revision. Concentrate on gradually reducing the ones you get incorrect.