Yeah, it is back and forth and in effect the back is an edge trailing stroke. Do it but don't use much pressure and the slurry will more of less stay for ten back and forths. When you get done with the one side move the water/slurry with the spine and begin on the other side. I don't use them as much as I used to. Now I rely more on circles and just go to x strokes but the back and forth can serve the purpose.