Exact same predicament here: VERY hard water, dries stupid fast; panel wash/dry with my black car and wifeys dark grey Grand Cherokee; top down was pattern; wipe down overspray onto previous panels; continue till complete. Farg’n PITA to make it come out looking right to my spec’s. I hit them both with the “wax as you dry” which helps a ton.The wife's Lexus was black. While it looked great clean, it was a real chore to keep it that way. I had to be very particular when detailing it, especially since we have really hard water here. I'd have to blow it off and immediately pull it inside to finish drying. Then, hit it with quick detailer to make sure I got any remaining water/spots off. And it you weren't meticulous with your quick detailer, it would streak like no other.
My white F-150 by comparison is a breeze.
The silver truck on the other hand…”easy as your white truck” Easy like Sunday morning!!