Well, the secret spray is usually a large container in which I mix mostly canola oil, some tuna fish (in oil), and all of the Friskies fish flavors: salmon, whitefish, Seafood entree, etc... I blend by hand until there are no chunks or I pour off the top once the sediment has settled. I'll cut it with some water, but the purpose of the oil is that it retains the smell of the fish, but is water resistant and won't dry-out as quickly.
This usually is too thick for a spray bottle, but I take it and I splash the walls of the abandoned building near the trap. I also pour some of the oil through the mesh bottom of the trap (leading in). I try not to pour it onto the ground (I don't want the cats tearing through the leaves trying to eat small morsels), but I try to mark the overall area of the trap with the scent.
I suppose if you REALLY wanted to get cats into the area, you could do something similar, soak a rag or cheesecloth in it, wrap it around some smelly fish from the fish market, and hang it in an onion bag by a string. Hello, raccoon central!
This may seem like overkill, but it's been working for me, and I never argue with what works.
I haven't seen the white cat in two days - about 45 minutes after marking the building this way, two cats showed up. The white cat was pawing around for an hour, obviously fixated on the smell, but the trap wasn't set.