I've used lemongrass oil before. can't say whether it helped. I think I would go with hive debris or some used top bars over the oil, but I know some folks swear by it. queen pheromone lures are also an option, and not terribly expensive. I'm not sure how the commercial version is made, but plenty of beekeepers make their own by dropping queens into a vial of ethanol. all of these lures
should be compatible with the others, though I'm not sure whether combining them will improve your odds or not. at the very least, it shouldn't hurt your odds unless you go way overboard with one of the lures.
when they work, bait hives are really great, but my success rate hasn't been very high. low effort, though, so it makes sense to put as many out as you can build and keep track of.
in my
experience, the most reliable way to get a swarm in a box is to put it there myself. or on a ramp leading into the box, at least. do it in the late afternoon and they're unlikely to take off again before dark. once they've spent a night, they don't often decide to abscond.
if you do use lemongrass, melting some into a lump of beeswax can make a lure that lasts longer than just dripping it into the hive. I've also heard that the species of lemongrass you choose could be important.