I bought one of these one time thinking wonder if it'll do anything. I mean I flush out my tank at least 1x/year. Emptied the tank, and in spring dewinterized the trailer and while doing the normal spring tasks, while I was doing water items I connected this to the hose and inserted it into the tank drain plug opening.
Keep in mind I flushed it out in the fall prior. The scale and such that came out using this very much caught me by surprise.
My only issue with this linked tool is that it's very flimsy plastic and mine broke after one use, but it did blast a heck of a lot of stuff out of my heater that I would have bet money on that none or nowhere near as much would come out.