You can see the bird dirt quite easily at 25 feet and even quite a lot higher. You treat it in the same was as you would if you were squeegeeing the window, wet it, let it soak in for a minute or two, and go back to it again. You also have the advantage of brush bristles instead of a soft pile on an applicator, so it is much easier to clean.
Sometimes if the bird dirt is baked on and is really stubborn, you may find that the particular window will take as long as it would take to do a clean window with a ladder and a squeegee. You are still safer though, and you will still save time on all the windows that don't have stubborn bird dirt on it.
You don't detail with a water fed pole, there is no need
Peter