Ever had a job where the brush just didn’t cut through the crud? Would you like to try something else? How about a pad based on special abrasives harder than the crud but softer than the glass. SRC Chew Pads for WFP work. No brush needed. Plus they help to make the glass hydrophylic. I can send you some flat felt treated with a slow release coating based on a plastic compositional abrasive right now. I will have to limit these however. And need to know what dimensions you want.