Blipping the throttle to the precisely matched rpm is no doubt an acquired skill, but if done properly it affords a silky smooth downshift. One might argue that this technique is not needed on a modern synchronized street car in the everyday driving. Yes and no.
A case in point: you are in 4th doing 70mph on ice or on packed snow. Suddenly, you need to stop the car in emergency (a fruitcake in an automatic SUV thinks that she's invincible and plants herself solid into a snow bank, blocking the road with her ugly bath tub on wheels. I see this happen every winter). If you hit the brakes, you're history. You need to drop 2 gears and then brake with the engine. The trouble is, at 70mph the gearbox ain't gonna let you engage 2nd no matter how hard you pull that stick. OTOH, you can do it easily if you know how to double declutch properly. This technique has saved my butt more times than I care to admit. I habitually double declutch at all times in any weather and although I would be first to admit that this is not always called for, this habit of mine is probably the only reason why I have never had a single gearbox breakdown on any of my cars. Ever. One more tip: always depress the clutch fully to the floor, enabling a complete disengagement. This saves your disk/basket.
i learnt my lesson