DIY or DIW?

Do it Yourself, or Doing it Wrong?

http://wowthatscool.com/-peachykeen/omgitsnotworking

Good one! Innovative for sure!

Yep. Sometimes, "whatever works" doesn't!

There's never time to do it right, but there's always time to do it over!

As a person who has worked with optics most of my life I shudder That rear window is probably toast (excuse me, frosted) by that nice abrasive dust, not to even mention what that brush can do.
Then, if that glass is "hardened/tempered" safety glass---once that hard shell is broken, the glass is weaker than plain old window glass.

That's one expensive, temporary, repair.

Enjoy, the car owner sure won't
JimB