When it is on a foot or wing, I usually recommend pulling broken blood feathers, as even if you get it to stop bleeding it's very easy to break back open in these locations. Strong tweezers will work, but even better are forceps or needle-nosed pliers. Pull straight out with firm and constant pressure. The chicken may cry out (it hurts!!) but it will help her heal faster. Apply gentle pressure and a clotting material (believe it or not, powdered cayenne is great for this, as it will help clot and has some antimicrobial properties) until any bleeding stops, then keep an eye on the foot for a day or two. She will re-grow the feather in its place.