Hi. I only did a bit of familiarization with my ds at home, from September before the exams in Nov(KE grammars) and Jan(KES). He has been offered places at KES and CHB.
However, I did a couple of NVR and VR papers with him around easter last year, just to see how he did. He got over 95% in the NVR first time that he tried, so I decided he didn't need my help to pass this one! He got around 75% on the VR, so we read more over the summer, and I tried to make him focus a bit more clearly on what he was reading, whatever that was; we talked more about the things he read; I encouraged him to read as wide a range of material as possible - newspapers, magazines, comics, factual books, as well as the fiction I love ( I usually read the fiction to him at bedtime!).
I suppose you'd call this a sort of English enrichment programme, which was easy for both of us, very enjoyable for both of us.
By the time we starting looking at papers together, in September last year, his vocab was better, his thinking was less, well, fuzzy. We found that there were 3 or 4 VR question types he disliked more than the rest. I focused on the questions he did like first, so his confidence improved, then tackled the ones he didn't like.
It was fun, not at all stressful. But he's a genuinely clever boy, and always had a good chance of success. All he needed really was nudging and more confidence in English.
What you do depends so much on your individual child. And no-one knows that child better than you!
I went by my instincts with my son. He would have been bored and irritated if I'd done lots of extra work with him in maths and NVR. He would have lost confidence in his English and VR unless I'd taken a gentle approach - boys can be so touchy about things they're not good at!!
What he and I did together worked for him because I know him so well ( we know a song about that, don't we, boys and girls - sorry
My advice: know your child, and make whatever you do fun