Lathe would be preferred of course but if your hand timing isnt off much, its really not hard to do and of course no need to ship out a bbl and pay a smith, etc.
Just make sure you use a triangle file, as you dont want to bump againt the threads when going around the face.
I saw on the fal files some dudes were using sanding discs cut out for the bbl but enough there for the bbl face to get worked, and basically putting disc on bbl, screwing into receiver and using the receiver as a support for sanding the bbl face.. Never tried this method.
Either way just go slow, go evenly and check often.
Make sure your handgaurd retainer is on before cranking it down too.
Once you have it timed the rest is cake.
Also, before you press the locking shoulder, check the tabbed end to make sure it fits into the receiver recess first. I almost forgot to check, and it turned out it needed to be filed down a smidge otherwise it wouldnt have gone in the recess all the way.