Is it posible you might be mistaking double-clutching for 'heel and toe'.

Like you described and I agree, to properly set yourself up to exit a corner, racing or other, matching the engine speed with the tranny is a must.
If it is done under braking, the method you are using is called heel and toe. You are blipping the throttle to match rpm's so that there is a seemless transition between gears.
Double clutching is for trucks and vehicules with no synchros, who have a hard time finding the next gear and engaging it smoothly.
This method is a big waste of time for racing and is not used with current cars.