When your in your chair you can feel and listen to the drag on hphobic glass, there is no slip and the rubber pulls and judders on the glass, but at the heights you work ther should only be glass that sheets, so you should be ok. I would start taking notes. If you intend to change over some day, use only gg3/gg4 as there is no salt in it and makes the transition to wfp easier. Cheapest way to experiment is an agri pump sprayer and buy some water, I think thats how Gary Mauer started. Wfp is faster but the higher you go the harder it gets. Unlike chair work you cannot do it all day.