Normally, I recommend using compressed air to blow out the felt.
I do that at every oil change on my customers vehicle. This is because in the NE, its just sand everywhere.
Normally, if this simple guideline is met, you will not have a problem.
Plastic knife in between the outer sealing strip and the window, and you can see the felt guides.
GM World Class Certified Service Technician. Chevrolet Professional Service Guild. Museum member #7993.