When you get it chop about 1/4 of it off for the windows and save the rest for the paint in a zip-loc. keep the surface wet (the cinnamon smell of the mothers doesn't give you the laquer thinner buzz but is nice) and keep kneeding the clay bar like you would a chunk of silly putty. It will pull over spray and spots right off the glass or paint finish and leave it very clean and smooth... The only time I've seen it not remove water spots it took polishing the glass with scratch remover to get the spots out...
