Martin wrote:
So I guess what is /really/ needed is a happy medium, where you can use the
instant recall to apply to the more general method, if that makes sense.
Unfortunately there seems to be only so much one can cram into a little
brain at a time!
In real life being able to instantly recall a product is better than knowing how
to derive it from scratch.

I totally disagree. If the 'instant recall' is outside of the small list
you have learnt, it's pointless. You need /both/ to be most effective.

(perhaps I should start playing times table tapes to the boys at night
instead of the Gruffalo!)
I learnt mine in the bath.

I remember 'completing the square on a generic quadratic from first
principles' suddenly clicking whilst I was in the dentist chair having a
tooth removed ...