Although airbrakes can slow you down, their correct usage is to aid steering, not reduce speed. That's the reason why you have a left airbrake and a right one. They work better if you just tap then (just one of them) slightly before the turn. I never ever use both brakes at the same time. I don't know if others do it with succes, though.

In case you doubt if a turn should be taken without braking I'd say go for it. Finding a good racing line is usually faster than braking but it is true that some tight turns will be faster if you can corner thanks to a slight tap in the brake.

Anyways, airbraking is something one must learn by himself. Some pilots here even use a technique of counterbraking (left brake for some right turns and viceversa) but I don't really use it.

PRACTICE LEADS TO PERFECTION !