It is really easy..once you have the knack for it. I cut the baffles for my sump. The first three cuts I made, I made a mess of and ruined the glass. After that I figured out how to do it so I ended up with a clean cut.
I scored the glass, and then grabbed the glass on either side of the score, and lined the score up with the edge of my work bench so that the score faced me. Then apply pressure, the glass easily snapped along the score. Once I figure it out, I cut three baffles down to size (six cuts), inlcuding one cut that was twenty two inces long. No problem.