I just got finished doing this today as I was removing the windshield and rear window. I purchased the tool from Ricks First Gen. I will say that it looks like the tool above would work the same. It can be a bit tricky especially considering the amount of junk that can accumulate below the trim.
I managed to get the rear window out without any problems (apart from the shock of discovering a severe case of cancer in the lower panel). However, I did chip the edge of the windshield. The above warnings are well founded. I had already planned on replacing my windshield as it was heavily scratched by the previouis D.A. owner who ran his windshield wipers without rubber on them for I don't know how long.