fst4dr nailed it.
I do a slightly modified version of speed shifting.
I let off the pedal to around 1/2 to 3/4 (you can tell by sound or rpms) as I tap the clutch pedal and quick shift.
This way the engine doesn't repetetively bounce off the rev limiter (fuel/spark cut) yet still keeps the throttle open and the air/fuel flowing.
It also let's the rpms fall a bit to a lower level and is easier on the syncros trying to match speeds. (thus faster shifting)
If you can really drive well
(Practice!) you can speed shift and rpm match instantly thus be able to shift faster by doing most of the syncros work for it. Plus you have less chance to hurt it.
