“If I can shapen a scythe I can shapen a two man saw.”
Maybe. Probably poorly unless you happen to have the right files, and the right jig to hold that beast so you get consistently correct angles. And some experience.
Best way get the experience is to acquire a new or old two-man saw (the one I bought new from crosscutsaw.com came in horrible shape and required hours to fix). Most old saws have been used and abused by amateurs so they need a bunch of fixing as well.
I couldn’t find a jig that allowed me to maintain the same angle when turning the saw around to work the alternate set of teeth, so I had to build one.
One of the “barterable skills” I decided on was sharpener of manual tools. Scythes, chisels, various drill bits, hand saws, clippers and shears, scissors, knives and swords. Each has special requirements and tools, along with consumables that need stocking. A stack of spare Tormek grindstones doesn’t come cheap, nor do files in boxes of 10-20 per size/style. Then you have to store them just as carefully as storing guns because they will rust with any significant humidity.