This may sound crazy...
Has anyone used like a garden sprayer (for like weed killer, etc) and filled it with distilled water and then used it to spray the car down after a thorough rising as a way to get a spot free rinse? My idea would be buy distilled water (or maybe it has to be deionized which would suck cause it's expensive) and use the sprayer only for water. It would seem that the spray would be similar to spot free rinses in autowashes.
Tell me how nuts this is and why it won't work. Because if you don't, I might just go waste my money to find out.