My Gummi Phlege experience
After thoroughly shaking, I pulled off the foam applicator head and transferred half the contents to a separate small container. Note the instructions to shake the container before using, this is very necessary as the liquid separates into two layers that require mixing.
Using a piece of cloth held in forceps (small taper nose pliers or strong tweezers would do) I applied the liquid inside the window seals, the mirror 'gasket' and inside the window groove of the door seal. The outsides of the seals were treated using the foam applicator supplied. I did this 3 times leaving a day or more between applications.
Before treatment I had wind noise from both windows near the mirrors, after treatment there was no wind noise at all from the passenger side and much reduced noise from the drivers side. Another and more important effect of the treatment was that previously it was necessary to slow down to 50mph in order to close the drivers window properly, now the window closes properly at 90mph.
If the windows are out of adjustment Gummi Phlege is unlikely to be of any use, but for wind noise with correctly adjusted windows it can help. Regardless of adjustment, Gummi Pflege does rejuvenate the seals and could be expected to make them last longer.