Fastest way to learn how to double clutch while down shifting?

Watching Fast and Furious, eh?



1. Push clutch pedal down
2. Shift to neutral
3. Lift clutch pedal up
4. "Blip" throttle to raise engine speed, "engine half" transmission speed
5. Push clutch pedal down
6. Shift into lower gear
7. Lift clutch pedal up

 

What the hell is double clutching? What is it supposed to achieve? Slowing down? I mean, why would someone shift down to go faster?

 

Higher revs give more acceleration. Have you ever tried pulling away in third gear? Yeah, it's slow innit.
You shift down to overtake someone quickly on a single-carriageway road. However, I've never heard of double-clutching either...