This will be a new skill that I will really enjoy practicing. I watch other divers to see what they do, I had not seen anyone employ that particular move but maybe I missed it somewhere.
Heh, I'm afraid the majority of OW instructors can't do this one

There's two parts that you have to master - the first is the 'power stroke' that moves you backward, the second is returning your fins to the starting position for the next stroke without pushing yourself forward again.
The first part can actually be best practised without fins - it's your legs as much as your fins which provide the backward thrust. Get in the pool with a snorkel and mask and practise the power stroke until you can easily move backwards. Then it's time to put the fins on...
For the second part you just need to slowly sneak your fins back through the water so it doesn't notice
