For the downshifting, you can speed things up if you spin up the input shaft by putting the gear selector in neutral with the clutch engaged (foot off it) and rev the engine to increase the speed of the input shaft, then clutch back in, and select the lower gear (now with the input shaft going faster [as is needed], the synchros have much less work to do to engage the lower gear).
I had an old Alfa Romeo that was fantastic overall but had a pretty terrible transmission, especially when cold. You do learn quickly how to get by. :)
This works for upshifting too, it's known as double clutching.
If you have a turbo diesel it's a good skill to learn as you can shift smoothly while still keeping the turbo spooled up and not cause as much wear on the gearbox.
I had an old Alfa Romeo that was fantastic overall but had a pretty terrible transmission, especially when cold. You do learn quickly how to get by. :)