I use a very popular type of brush from a very popular supplier but am finding it is leaving very fine scratches on some glass. Not all and it isn't coated glass either. It is a medium mono filament brush. Anybody found the same? It isn't grit in the brush as it has had a thorough clean. I only notice it when the sun is on it at a certain angle but it could be an expensive job if the customer notices. Up to now its been on upvc glass which im told is softer than glass used to be. I'm thinking of moving to flocked as maybe the monofilament is too harsh. Any thoughts?