Centrarchid, I get what you are saying about already baiting but I do think keeping a trap set with a strong smelling bait does risk luring in something that may not have stopped to investigate a closed up coop... I would definitely bait however if I had already suffered an attack. I used the carcasses of the chickens killed by the raccoon family as bait (very successfully) after they killed the three birds last summer.
Bait can be something like wet chicken feed or broken egg. These items almost always present at least as traces where ever laying hens are kept. I also use chicken carcass as "big gun" once predation realized but sometimes that can bring in others that were not original culprits.