I haven't used GS27, but i've used a similar product. Meguiars scratchX. It doesn't really do much at all. Very fine scratches, like something you setting your keys on your car (not keying) should be able to come out. But really it doesnt do much. I imagine GS27 is the same. It should just go on and come right off. It may slightly dull the paint because of the abrasives in it. But a light polish or wax after should clear that up! Good luck to you