Encouraging Bees to Move Downward
I have a hive body with drawn out combs and a nuc box sitting on top of it with a hole in its bottom that matches a hole in the inner cover that is atop the hive body. The nuke contains a small swarm which I would like to encourage to go down into the hive body. The swarm has been in the nuc for about 24 hours.
The easiest way is to move the frames from the nuc to the box. We have done that a couple of times this season. Trap the swarm on a nuc, set the nuc on the new location, and once they settle down on those frames, we just move the frames into a deep box and remove the nuc.
In the case the box below has a different frame size or top bars, then you will certainly need the setup you currently have.
You could set a syrup feeder in the box below and if you have any Honey-B-Healthy or Pro-Health, you could mix with syrup (following label instructions) and spray over the comb on the bottom box. Bees like the smell and will be encouraged to move down to take the feed and once they spend time there they're more likely to move faster.
Over time they should move down. They always prefer to move up, but there are some bee management techniques where the new equipment is added underneath (and not on top of) the bees. For example, the Warre hive management asks for a new (and empty) box to be added to the bottom of the existing colony (and the bees will move down and occupy that space).