Originally Posted by L&AirC
If you look at any of the online videos of people sharpening edges, except for when using a file, they are usually using a back and forth motion. You don't do this with a file because they typically only work in one direction.
Yep...with diamond stones (use a water based lubricant such as svst's secret sauce or just water...not oil based!) you would use back and forth motions, short laps for the first pass or two, increasingly longer laps until you finish with 3 or 4 full length passes tip to tail, tail to tip, for each of the 4 side edges.
As far as filing itself is concerned, they are only one direction, but every tech I personally know or have read about (as well as myself) uses a lapping technique with the files as well; short laps working your way up to full length passes (this ensures an accurate, smooth, and sharp edge). But again, you may start filing from the tail (unless your ambidextrous ), there's no harm to be done, performance wise