Double clutching is mainly used in road racing (correct me if I'm wrong), but in TF&TF it was used in the wrong context.
As previously stated, double clutching helps get everything in 'synch' better. 1-2....As shifting from one to two, as you are passing thru the neutral gate, let up on the clutch, as you go into second again push it in. That in short, is double clutching.
I think Mamba was trying to refer to 'rev matching'. Which is while downshifting, pushing the gas pedal to where the RPMs will be when engaged in the next lower gear, which gives you smoother down shifting.
Powershifting, is keeping it to the floor while shifting. Some like, some don't. I've had good success with it.
As for launching. Play with it. 2500-3000 is about the best with a little clutch slippage.
