Problem is that there is still debris on the paint. Driving off will cause the remnant water to slide off. While it is sliding off it will trap debris/dirt and scratch. Swirls will form.
Best way is a proper car wash method. Check out gilmour foam gun for a regular water hose. As I said before invest in two buckets and grit guard and put some elbow grease into your car. You are paying a grand to make it new. Why not put a little effort and some chump change to keep it that way.
Weeks worth of rain, yes ONR still does wonders. Do a panel at a time. Caked on dirt/salt, then rinse off thoroughly before ONR or using a foam gun.
2012 BMW 128i 6MT Deep Sea Blue Metallic