Hmmm, I disagree, the whole concept of double clutching is to get the gear box spinning at approximately the same RPM's as the engine for the next gear, hence the throttle blip when in neutral, so you sentence should read ....
Double Clutching would be pressing in the clutch, releasing it in neutral, blipping the throttle, then pressing down on the clutch again and then shifting to the next gear.
Try it, you'll see what I mean, get that next gear spinning at the right RPM and then get mesh not mash.
You are right about getting the engine and trans speeds to match.
You are very close except you only need to blip the throttle when downshifting,so the engine rpm meets the rpm it will be at when you grab the lower gear.
When upshifting ,you are actually waiting for the engine rpm to come down [usually about 400-500rpm less than ]what you ran the gear up to.If you hear a throttle blip while upshifting,it is because they missed the gear by a second or 2.
If you wound a gear up to 1600rpm ,you go in the next gear when the engine drops to 1200rpm.
Down shift is the opposite ;slow down the truck until you reach 1200rpm,clutch,rev motor to 1600 rpm,clutch,engage lower gear.
The #s I used are apr. not exact,as all trucks are a bit different.