I'm of the opinion that wounds heal and skin grows best in moist conditions. I might be inclined to use a combination of honey and sugar, but then I'm a beekeeper so I'm always keen to encourage the use of hive products as they have incredible health benefits. The honey will help the sugar to stick to the wound and keep it moist whilst allowing the sugar crystals to do their work. It should also prevent any more feathers from getting stuck in the scab and pulling.