I think that it's both the smell and taste which keeps other chickens from pecking. My self-picking hen doesn't like the taste but keeps pecking anyway.
What was the item that you purchased and how is it working? I have a hen who picks on herself and I've tried a number of things - sulphur for mites, Pick-No-More, extra protein, Nu-Stock, garlic spray. The Pick-No-More and Nu-Stock work at deterring her but I hate to keep either one on her...