If you shoot a selfbow without an arrow shelf, you may have experienced feathers cutting your finger. Worse, you may have run a quill a ways into your finger. This happens when the leading edge of the lower hen feather is slightly lifted off the arrow or has a sharp edge to it.
Even with careful trimming of the leading edge of your feather, wear and tear on the feathers from regular shooting can eventually create rough or cracked edges. You can reduce this by taking a round piece of metal and rolling it back against the feather. This will compress and smooth out the leading edge of the feather. Any round metal object, such a nail, screwdriver, et cetera will work.
John Strunk of Tillamook, Oregon, always used an arrow with a field point on it. In between targets while attending the North American Longbow Safari, he would constantly roll the side of the field point along the leading edge of the feathers of his target arrow.