We have super hard water here and do most of my washing/detailing at my work. So for the last 5 years I've been buying distilled water by the gallon at WalMart and have a dedicated plastic garden sprayer that I use. After washing the car, I can "rinse" the whole car with about 1 gallon of water (under $1.00) for a spot free shine. I just washed the Hummer on Tuesday and used less than one gallon for rinsing.
One of the tricks I use to avoid "trickle trails" is as soon as I'm done washing the car, I use a portable Makita blower to blow out the water from inside the mirrors, door jams, nooks and crannies. Even if washing the car with mineral free water, these nooks and crannies can let water drip out later that may have soap residue, dirt, etc in them that leaves trickle stain on the paint. After blowing out the nooks and crannies, I then spray the car with distilled water and finish up the detail.
Cheers,
George