I've made a number of hickory bows and I find water based polyurethane to work just fine. Wipe it on with a clean cotton rag, let dry, light sanding, then wipe on another coat. Buff with steel wool to dull the sheen.
As for stain, nothing beats walnut hulls. Pick up a few walnuts when they drop and crush the hulls while they are green. I just store mine in an tin can and use them indefinitely. They will turn black as they age. If they dry just add water. Wipe in with a rag until the required darknes is aquired.