If I were you, I wouldn't powershift. That can kill an engine quickly. Just use the clutch normally and shift smoothly. I found myself rushing from gear to gear and grinding alot. That is slow. When you grind, your times are worse because that grinding is losing power. Remember, smooth is fast.
As for the double clutching deal, that is an old technique. It isn't really used these days because the sychronizers are pretty good about keeping up. Double clutching is just slower now.
The rev-matching technique is very nice to learn. It is so cool and no one expects how smooth it is. I don't know how well it works in MP3s but in my integra, if i am crusing at about 45 or so in fourth gear, put it in neutral and rev it up to about 4700-4900 RPMs then put it in third, I get a PERFECTLY smooth acceleration. No rocking, or jolting. The car just sucks you into the seat. Rev Matching requires you to know your car VERY well. It also preserves your transmission because you are doing all the work. I don't really know how to describe in words how to do this, you kinda have to learn on your own. If you get good enough, you can use it to slow down like the professional drivers which can save your brakes. DAMN DRIVING IS FUN! You learn something new everyday.