One toolmaker to another a flat file for the depth teeth, the correct diameter round file ( I use Sandvic ) for the chain size, same number of full strokes on each tooth, and a little practice you will be fine. Stihl chain has the angle etched on the top of the tooth but if you give the chain a few strokes after every tank a fuel and don't hit anything with it you can lay the file into the tooth and get the feel for the angle before you start. Get a depth gage for the depth teeth. Turn your bar over when you feel a wire edge building up and flat draw file the top surface of the bar the lightly break the edge
I use Grobet files when I can get them. Pricey but best I’ve used.
