Paddling backwards technique is much the same as reversed forward paddling and can also be used for reducing speed in waves or when approaching for a rescue. Because you'll most likely need to paddle backwards just a few meters, the style doesn't matter so much as long you maintain your balance.
Paddling backwards can be tricky, especially if your kayak is equipped with a rudder. In such case press the both foot pedals to keep the rudder straight. Also, stern-heavy kayaks can behave unpredictably when paddled backwards, a problem you can overcome by leaning forward in the cockpit to lift weight from the stern.