Tom, a polyurethane based penetrating sealer, with or without stain, and a spar urethane or gasket lacquer top coat will do a good job. The only disadvantage to the urethane top coat that I've experienced is that it makes the arrows difficult to pull from 3D targets.
On the set I finished today, I used two coats of Minwax penetrating sealer with "natural" stain, followed by 4 coats of nitrocellulose gasket lacquer. I steel-wooled them lightly after the first gasket lacquer coat to smooth a little rough grain. Each coat is thin, and after 4 it gets an even sheen.
I crested them with craft store paint and Sharpie pens in three colors. I sprayed the cresting with a very light coat of acrylic lacquer and glued the fletching on with Loctite superglue. Over the lacquer, superglue needs about 20 minutes drying time. Over urethane, 5 minutes will do it. I finished them with a drop of Duco cement at each end of each feather to anchor them and hopefully keep a loose fletching out of my knuckle.