[xracerbob]

To get the most speed out of the car on a road course it is necessary to be able to master. As you brake for a corner, you want to be able to go back to power as you exit the corner (or sooner) which in most cases will require a down shift or two. Since you are already braking on the threshold of locking the brakes, if you abruptly downshift and add engine braking to the rear wheels, you will probably spin the car. The idea with the double clutch downshift is as previously stated is to match the revs of the drivetrain to the wheels. You want to maintain a stable platform for the tires to do their thing; no pitching of the car fore and aft, no yanking of the steering wheel, etc.

The sequence for the down shift is:

Brake and clutch in, shift to neutral, clutch out, roll your foot over while maintaining brake pressure to blip the throttle, clutch back in, shift to lower gear, clutch out. Repeat as necessary.

It takes longer to say it than do it, once you "get it". I drive a manual car as a daily driver and do it every downshift out of habit. I used to teach this at Skip Barber's school, and some people struggled with this even after they did some race series events, but then it just clicked for them and they were suddenly faster and more relaxed. Plus it's just a lot more enjoyable to drive.