I had a chance to finally wash by Black sapphire metallic X5 after being coated with C1 and EXO v2 last February. Here are my steps and guaranteed did not induce any scratches or marring, panel by panel ensuring clean mitt and water
1. Foam, pressure wash, foam, then pressure wash
2. Foam, with high quality sheepskin mitt, lightly, top to bottom, 2-bucket
3. Use water bottle to sheet water
4. Shop-Vac with tiny nozzle extension to blow dry
Rinse and repeat on each panel, inspecting paint work every panel
I had a hard time correcting the paint work on this BMW paint and took me at least 20 hours to do it so I am avoiding any swirls and marring as much as possible