Here in the U.S., all the commercial window cleaners use a squegee for removing the water... I asked one what he used in the water and, after glancing over his shoulder as if he was revealing a family secret, said in sotto voce, Ammonia... I've found an ammonia product that smells like lemon and absolutely doesn't streak, but needs to be used with the squegee (live rubber preferably, mines 14 inches across and fits most windows). I usually run over the windows lightly with crumpled newsprint afterward since the ink leaves a nice shine...