50/50 chlorine mix. Test in a hidden area. If it’s a good paint there should be no discoloration. Spray on lines and rinse when the lines disappear. 5 minuets and walk away with however much money it would cost to power wash.
Depending on what the streaks are, a 50/50 Chlorine mix would take most stuff off. If it is rust though, try using Oxalic Acid. Be sure to rinse super good though. And if you use Oxalic Acid, don’t get it on any windows!