have a look here.
Tom Seeley explains how bees decide where to live.
You can see how scouts investigate a cavity and how they communicate what they find and recruit the rest of the swarm. Good stuff
My bait boxes are 40 litres with a couple of smaller ones which are good at catching casts.
They are all painted inside with propolis. They have a starter strip frame against the far end and an old brood frame next to this. The entrance is a round hole about an inch in diameter. The top bars and entrance are anointed with lemon grass oil. I put them on shed roofs etc. The never fail