I like Dawn’s simpler solution.
I think what’s most important is to ensure the flow back gap is open. I check those weekly on my flow hives, and occasionally there has been some honey collecting. If it’s fresh and your hive is at the correct angle, it will flow slowly back into the hive and you can see the bees lapping it up from inside.
I’m not sure if the bees would get sick if it had been sitting there for a while and had a chance to ferment. If that would be the case, rinsing the channel might be the better option. I never had to do it.
Don’t forget to scrape the wax off the little closing disc sometimes too.
The flow hive angle and a clean pathway are important for that genial flow gap to work.
Before harvest, I wrap a slightly damp double chux cloth (off the chux roll) around the flow key, insert it into the collection channel and twirl it while retrieving.
It’s probably not necessary, but sometimes I get some wax flakes out.
Make sure you don’t loose your cleaning cloth in the channel. Happened to me once, but got it out with a long wire with a hook at the end. Won’t happen again.