It's the blip I'm not really getting I guess. My downshift from 3 to 2 is not a happy movement yet.
Okay if you are mechanically minded, this is what you need to visualise.
Inside the gearbox, when you're moving down into 2nd, you need the engine-side of the gearbox to be going at about the same speed as it will need to be going once you've dropped into 2nd, BEFORE you stick it in 2nd.
So, your target when you double-declutch into neutral and then "blip" the throttle is you put the engine revs at just over the engine speed you think you'll end up at, before you put the clutch back down again and ease the stick into 2nd.
I say "just over" because in the small time between the throttle "blip" and getting into 2nd, the front half of the gearbox starts slowing down with the oil viscosity, so you ideally account for that.
In time, you'll also find yourself compensating for
- How hot the gearbox is (how long/fast you've been driving). When cold, it slows down a lot faster, so you might need a bit more "blip" or to be quicker. When hot, you need less "blip" or you need to wait longer after the "blip" if you overdo it.
- How much the vehicle slowed down while you made the shift. Depends on gradient etc.
If you can imagine those engine-side cogs spinning, and how they ideally need to be ending up at the same speed as the "output" cogs before engaging, it all makes sense.
Also think about the noise a big old lorry makes, or used to make when you were younger, when downshifting at speed to take a hill. It sounds like it's all for show, but it's all based on a practical necessity.