It works a bit faster if you do it edge-leading, but you get the same results either way and you're less likely to make a mistake if you do it edge-trailing.
I'm not really a sharpness fanboy so I'm not sure I'll be doing this on every razor but it certainly kicked this one example up to where it needed to be.
I also recall it working faster if there were a photo on the top sheet, I think the ink really helps.