If flashcards are a revision method that works for you then they will help you achieve your grade. It is important to find revision strategies that are effective and you retain information from. For example, no matter how much it was drilled into my head, making flashcards never helped me. I didn't find them useful. I didn't retain the information. If you're absolutely sure it works for you, use it though.
One thing to keep in mind is that memorising the content on the flashcards will only help you if you're asked to recall that specific bit of knowledge. If you're given an application of knowledge question (these will change each year and are difficult to revise for) and you don't have an in-depth understanding of the topic, you may find you lose marks. So for that I would suggest you also consider doing past papers which will cover both straight knowledge questions and get you plenty of practice at applying the knowledge to different situations. You'll also gain a wealth of exam technique which is very beneficial at countering nerves as well getting you that grade on exam day.
Doing the past papers would be the best revision strategy in my opinion and is what got me to my grade 9. There should be plenty of time to get through them all between now and next Summer too. Good luck!