I use Two Ton epoxy, the two tube type. I squeeze equal amounts of hardener and resin in a baby food jar, about 1/2 teaspoon of each, fill the jar about half full with acetone and mix everything up with a popsicle stick, mixing is easy and quick. I mix a small amount and use it up before I mix more as it will only keep for a few days before setting up.
The above mix is enough to finish a bow with 5 or 6 coats, I once used it on arrows as well but have gotten lazy since.
I use a small square of Tee shirt to apply the finish, you only get one quick swipe before the epoxy acetone gets tacky. I let a coat cure overnight unless it is really hot out in my shop at which point the finish cures quickly in a couple of hours.
This is the most durable finish I have ever used, i can loose an arrow under the grass for 6 months, the feathers will be toast but the shaft will still be pristine, moisture doesn't get through this stuff.