Feathers were apparently used several different ways. The is one early 19th century account of loading where the feather is inserted in the touch hole before the charge goes down the bore and is then pulled when he was ready to prime.
Audubon watches his host prepare for a night of raccoon hunting:
"… He blows through his rifle to ascertain that it is clear, examines his flint, and thrusts a feather into the touch-hole. To a leathern bag swung at his side is attached a powder-horn; his sheath-knife is there also; below hangs a narrow strip of homespun linen. He takes from his bag a bullet, pulls with his teeth the wooden stopper from his powder-horn, lays the ball in one hand, and with the other pours the powder upon it until it is just overtopped. Raising the horn to his mouth, he again closes it with the stopper, and restores it to its place. He introduces the powder into the tube; springs the box of his gun, greases the "patch" over with some melted tallow, or damps it; then places it on the honey-combed muzzle of his piece. The bullet is placed on the patch over the bore, and pressed with the handle of the knife, which now trims the edge of the linen. The elastic hickory rod, held with both hands, smoothly pushes the ball to its bed; once, twice, thrice has it rebounded. The rifle leaps as it were into the hunters arms, the feather is drawn from the touch-hole, the powder fills the pan, which is closed. “Now I’m ready,” cries the woodsman….
I think this practice may have continued with target shooters in the 1920s who didn't want to blow any powder out the hole.
Other claim the were inserted when at day's hunt was over and the rifle was in camp. I learned the hard way that a rifle laying on the floor of a tent or lean-to can end up with a damp charge in the touch hole over night. Gary