The best thing I have found for quick field touch-ups while hunting, packing, or etc away from home, are the small diamond rod sharpeners. Several companies make them. I am talking about the small ones that fit in a shirt packet (or pack) like a writting pen and about the same size and weight. They make arough edge, but they are durable and work great and fast for a field touch-up.
You can dress up the edge when you get back home.