Hi!
I used to use the Stihl file guide, but when chain grinders entered my life, things changed. They are really, really great at restoring a chain to "factory spec" - however, it is not practical to drag them into the woods! Then I started cutting bigger, harder wood, and needed to maintain the cutters "in the field", so to speak. I looked up countless videos on hand sharpening, and spent days training my hand with a chain in a normal vise. I went to my local Stihl dealer and requested a few links of new chain which I keep in my box and use as a reference to compare my hand-filed chains to, to make sure that I stay "on course", and do not wander off too far from the ideal angles. Finally it began to come together. I now use a stump vise to hold the saw, and touch up the cutters every few tanks, depending on the hardness of the wood I'm, cutting. When filing, it's important to "over tension" your chain a bit to keep it from rocking under the filing stroke. When you are done, don't forget to restore the proper chain tension!
Buckin' Billy Ray has a few good videos (although he is a bit of a cowboy!), but he took the mystery out of the subject of hand filing, and made it accessible to us mere mortals, who do not necessarily earn a living from running saws ( he calls us "friends"!).
The best video by far is this one by Tips from a Shipwright and is to be found here: This is the most logical, calm explanation you will find on proper filing techniques!
To finish, remember the classic saying: "And O! But to practise!"
Happy filing and safe cutting!
Mike