If you have lost your balance slightly and are about to fall over, the low brace is the way to recover without even getting yourself wet. The prefix "low" here means that you keep your paddle below your elbows during the brace.
You can do the low brace by simply pushing the paddle against the surface of water or make it last a little longer by sweeping the blade against the surface.
First we will take the correct posture. Keep the regular forward paddling grip of your paddle. Put the paddle close to your hip and check that the blade's back face is pointing down on the side you are about to lean. This means that you have your elbows on that side quite high and knuckles are pointing downwards.
If the kayak would be moving, you would also need to check that the blade's edge that points towards is slightly elevated. This way, when you sweep it against the water, it will start to climb up to the surface instead of diving under the water.
To practise the low brace technique, lean to the side until you begin to fall over. After you have slightly lost your balance quickly push the blade down against the surface and simultaneously move your weight bravely on the paddle. Try to keep your paddle horizontal while bracing, since that way it will give you the best possible support.
your intuition might tell you to quickly bend your torso back on top of the kayak to recover the balance. But you are not on a solid ground so things work a little different. First you should righten the kayak and only after that, worry about your upper body.
The kayak is rightened by doing the hip flick that was taught in previous tutorial Recovery basics. Basically it means that you twist your hip and push the deck with your knee to make the kayak tilt back upright.
Now the kayak starts to be back to its level position. The rotating force of it will assist you a little, when you push your upper body back to balance. Think of it more as if the kayak would have slipped and you are trying to pull it back underneath you. Keeping your body close to the deck will also make things much easier.
Keep practising and after a while, try to add a sweeping motion from back to forth and you will soon be able to brace for a lot longer. And remember to practise on both sides.
If the low brace fails, you can try to recover your self by switching to a high brace.