Here's one way to make a gumpaste feather with a mold. You can do this without a mold, too, but I like the way the center quill looks when you use the mold. I made this one for my online shop and it's about 4" long, so it would work in gumpaste arrangements size-wise. If you want to do them with no wires just mold the feather and either leave it or cut the edges of the feather.
If you cut the edges use a sharp knife and kind of frill the edges of the feather, cutting through almost to the quill here and there.
Dry the feather on crumpled plastic wrap or something else that has a little curve to it so that the cut edges don't dry flat.
If you want to put it on wires, curve the wire to fit the shape of the quill.
Pinch the gumpaste around the wire so that it's secured, and remove it from the mold.
You can cut the edges the same way as the unwired one to give it some movement. Don't cut too much or it will just look raggedy. If you use a mold you want to maintain some of the texture from the mold itself.
You can do this without the mold, but make sure that you press a really thin quill into the center of the feather, not a big fat one. That will ruin it!