In my experience, it's even more precise to use multiple fingers at once. I use two or three on symmetrical trackballs like that. Using software for a scroll

In my experience, it's even more precise to use multiple fingers at once. I use two or three on symmetrical trackballs like that. Using software for a scroll button like that is often annoyingly flaky and inconsistent in practice, as too much software isn't expecting it or tries to do its own special thing (websites in particular for the latter). I haven't used a trackball that does it in hardware, but that may run into issues too, as a lot of software is built to scroll in whole numbers of lines, and so feels unresponsive to more precise scrolling methods (e.g. scroll button or touch screen).