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