For group hikes where we plan on having a fire, I carry a hand chain saw for dead wood. We've used ours for a while now and it is definitely getting dull. How do you sharpen this?
It sharpens just like a regular chainsaw, which is well documented, with one important difference. Since it cuts in both directions, the filing must be done to account for that.
For tools, you'll need a small vice to hold the chain steady while you sharpen it, and a round file. Ultimate Survival Tech (EXTREME PRODUCT NAME) recommends a 1/8" round file for their saws: