How do you keep bees from collecting in or on the containers while draining the hive?
Welcome to the forum, Edward.
There’s a number of methods used and described in the forum you could search for. In short, connect a short length of clear flexible hose to the Flow tube and direct the other end into the container through a hole in the lid cut slightly larger than the hose. This keeps the bees out while allowing air out.
Alternatively, you can drape a light cloth over everything, though this is fiddle in practice.
Some have made up a full on manifold system directed into a 5gal pail through a hole in the lid. I prefer individual frames drain into separate containers to preserve the unique flavours each frame often has.
Once you’ve setup your preferred method, you’ll enjoy harvesting honey much more.