Have him put a glob on a stick,take a good whiff, and write down what he smells. Go back and take a whiff of the same glob every 12 hours. Differant ingredients have diff. levels of volition in terms of how soon they dissapate from the mix. Over a couple of days, he may find that he can pick up on several ingredients that were too overpowered by other ingredients (to his nose, not the animal's) to pick out at first. He will never come up with the exact same mix, but may come up with something he has confidence in and that is probably almost as key as the ingredients themselves. Plenty of good commercial lures out there.