Actually, double clutching is just that, the clutch has to be engaged and disengaged twice with every gear shift. This was required on older vehicles and even some newer trucks before synchronized manuals were standard. An older Army truck I drove required this, and it was a PITA. Just try doing it for the hell of it. Shift into gear, then disengage clutch and out of gear, then engage clutch while in neutral, then disengage clutch and put in gear, then engage clutch. Yeah - fun.
For new cars, you donít have to match the RPM unless youíre really up there. Even then, you should let the engine RPM drop before taking it out of gear for a downshift. I donít care what that post says, but normal driving should not reach an RPM level that would be any problem for a downshift. If you hit your head on the steering wheel when you downshift, yeah, youíre doing it wrong.