Several years ago I was given a sample of a wheel-like device for finding alternate fingerings called Horn Harmonics. At the time I thought it honestly to be somewhat useless, as most alternates are pretty obvious. However, last year, I started using the device somewhat regularly in lessons to find a specific type of alternate fingering easily.
As implied in the rather long title to this post, what I found this product useful for was for finding custom stopped horn fingerings for some students. Specifically for students with small hands. I personally can use standard stopped horn fingerings pretty well, but for students with small hands they will tend to be sharp to very sharp. The notes can be blown down to a point but it causes real production issues for those players and is overall a frustration.
My students can confirm that I had the device hanging on the wall as sort of a decoration for quite a while. Then there was a day when I was working with someone on stopped horn and I thought to myself there must be a flat fingering for say B in the staff that would make it easier to play a stopped C in tune, and maybe that fingering is on that device?
Alternate fingerings that are flat are easy to find in the Horn Harmonics wheel. In the case of that note, the flat fingering would be T23.
In short, for any note in the treble clef or above there are flat alternate fingerings that work great as stopped horn fingerings for students with small hands. I find myself using this device at least every couple weeks during the semester to find these, and if you have small hands or work with students with small hands this is a great product. It just took me a few years to figure it out. For more information check their website; the device sells currently for $6.00.