I have used queen excluders on almost all hives for extracted honey and have made these observations; 1. When placing excluders on all hives over the brood nest, less that half of the hives will readily pass through and it doesn't sem to matter what is over the excluder. Yes, they will swarm rather than go through. 2. As you suggest, placing some brood over the excluder encourages the bees to pass through, so I routinely do that now. Once the bees are accustomed to passing through , one can move the excluder up over the brood nest. I routinely use a hive body and a medium as a brood nest and as soon as there are eggs in the medium I place the QE under it for a week or so, then put it on top of the medium. Jerry in PA