It is a shame you gave up. We could have easily walked you through it if you asked for help soon enough.
It really isn't that hard. As you said, the clean copy, the pixelated copy and the track matte.
Heck, you can use a garbage matte on the copy and avoid the track matte altogether. Just use the 8 point matte if you need more than a four point matte. Mosaic applied hides the fact that the matte does not have soft edges. If you need a second blur, copy the second track to the third track and change the location of the garbage matte.