I've been lurking on the side for some time reading in earnest and picking up a lot of great info from AS members. I'll admit right now I use a file guide when sharpening as I definitely don;t have the skill and experience to attempt freehand. The file guides are engraved with various cutting angles but aligning and holding the file thru the cut is easier said than done. To improve my chain sharpening I made a jig which has helped immensely. To start it's just a piece of plywood with the ends cut at 30 degrees in the shape of a trapezoid, a few lines scribed parallel to ends and then a block of wood attached.
Next my bar and chain are sandwiched with the jig in a vise. From here on all I have to do is keep my file level to the bench, canted so it rests on both the cutter and raker then extend my focus to the scribed lines which aligns the file to the correct angle.
This set up although not necessary for the pros is providing me with excellent results consistantly. It is quick to slide the next cutter anywhere near the scribed lines, doesn't have to be in any exact location, so long as you file parallel to the lines.
Another thing I've found highly beneficial as I begin filing each time is using a 5x eye loupe and view progress on cutting edge of top plate . Once enough strokes have cleaned up the cutting edge I give all the cutters the same number of strokes.
Anyway just wanted to share something that is easy to make and may help others sharpen their chains.