I think you should have described the procedure in a bit more detail to stop the uninitiated getting themselves in a total mess. Balance 1&2 together, then 3&4 together (or the other way round, it doesn't matter), then balance both pairs together with the middle screw. I always give them a little blip when I think I've got them right too as the pressure of the screwdriver can slightly unseat the slides off the stop and give you a false reading. Like the modern tool, I'm still on Davida needle gauges which are not nearly so easy to work with (but I am an old fart 😂) but you're right, you know when you're spot on because the engine suddenly sounds sweet.
