Sepp,
I installed mine without the tool. It was slow going. I used a paint can key because it was blunt enough to not damamge the strip.
It can be done...If I had to do it again I might buy the tool unless others say it didn't add much to the ease. I also don't have a 5 window. Just one rear window to deal with.
I had to tape the gasket to the window all the way around on both sides to keep it form flopping off.
Rich
