Owner Top Floats are extremely sensitive floats designed for still waters. They have thin bodies and multicolored bristles extending above the float body. They come in three sizes, 70mm, 85mm and 100mm. I have the 70mm and the 100mm floats in stock. I think the 70mm size should be ideal for sunfish in still water, while the 100mm floats would work better when you fishing with more weight and more bait.
Their very thin shape, together with the thin bristle, makes them extremely sensitive. To fish them properly, sufficient weight is added to your line below the float so that only the bristle, or even only a portion of the bristle is showing above the surface. With virtually the entire float under the surface, it is almost perfectly neutrally buoyant. Only a very small pull from a fish is sufficient to take the float under completely.
The Top Floats are much too sensitive to use on a stream with more than a slight current, unless your bait is well above the bottom. Rocks and other obstructions on the bottom slow the current near the bottom, potentially making it very different from the current speed at the surface where the float is. If the Top Float is shotted so that only the bristle is above the surface, just that current differential can at times pull the float under. I found that out the first time I tried to use porcupine quill floats in a stream. For use in any stream other than one with minimal current I would recommend the Owner Acorn Floats instead.
In still water, though, or in a slow flat water stream, you can add sufficient shot so that only the top, red portion of the bristle is visible above the surface. The slightest pull from a fish will take the float under.
Putting a small split shot down very close to the hook, called a "tell-tale shot", will allow the float to show what is called an "up bite," which is when a fish lifts the bait rather than pulling it down. If the fish lifts the bait or swims upwards far enough to lift the tell-tale shot, less weight would be pulling the float down and the float would rise slightly and you would see more colors of the bristle. An Acorn Float probably would not register an up bite, and a round bobber or Nakazima Ball Float certainly wouldn't.
Depending on what bait you use, and the weight of the bait, you may also be able to tell if there is no longer any bait on your hook. To determine the proper amount of weight to add to the line, you have to test it with your baited hook attached. If you add shot to the point that only the red tip of the bristle is showing when your hook is baited, when you no longer have any bait on the hook, more of the bristle will show. Of course, if your bait is very light, or very nearly neutrally buoyant, the float may not rise enough to see the difference.
Proper shotting of a still water float can be far more complex than I can get into here, but the primary thing to remember is to add enough weight so that only the bristle or even just a portion of the bristle is showing above the surface. With the 70mm Top Floats, three #6 Dinsmore shot may be sufficient, depending on the weight of your hook and bait. You might be able to add one #10 shot to that. Four #6 shot or a single BB shot would be too much. With the 100mm Top Floats, you may need two BB shot, or two BB shot plus one or more smaller shot, depending on the weight of your hook and bait.
The Owner Top Floats are light enough, and the shot required to fish them properly is light enough that you could easily fish them with a sieryu rod. We don't have herabuna here in the US, so I have not imported any hera rods. However, we have thousands of ponds with hungry sunfish, for which a seiryu rod is just ideal, and for which you could fish in very much the same way they fish for hera in Japan (although without as much paraphernalia). If carp or catfish are a possibility, I would definitely not use a sieryu rod, though!
I can easily see a lazy afternoon at a pond with a long seiru rod, an Owner Top Float, some Dinsmore split shot split shot and the bait of your choice. You could walk the shoreline, or you could bring a folding chair and some iced tea.