Ah! Black Paint care and feeding....
I agree with much of what NorthGTI states here. I have a few exceptions because they work for my and my 3 Black cars.
Point #1 "If the paint surface has "swirl marks", it is due to poor maintanance technic."
This is very very true. Every mark on my vehicles I know and I continue to work on. Dings, scratches from a coat or someone's carelessness.
There are a few things I'm going to add here. Use as MUCH WATER as you can. Flush off as much dirt and grime as you can. Start washing from the top and work your way down. If your bucket water looks dirty or if you are in a Salt/Winter conditions, CHANGE WATER before doing the sides of the vehicle.
If you drop what you are washing the car with, Mitt/Sponge/Towel, whatever, STOP put it away and use something else. NEVER EVER use something that is not clean on the surface of your paint.
Take care or your towels or product that touch your car. Wash them with NO FABRIC SOFTENER or BLEACH. All of my towels are 100 % American Made Cotton towels. Even the thread for the seams are cotton. Some of the off brands will use a poly cotton thread for the seams. If I find some of this, I CUT OFF the Seamed portions.
Do NOT wash Microfiber towels with Cotton Towels!
Use better quality products on your Finish. Basic Turtle Wax just won't cut it on a black vehicle. Use Zainos, Meguiar's, or my favorite Zymol Wax Products.
To keep a Black vehicle looking it's BEST, you need to wax it at LEAST once every three months. This is a MINIMUM. In the climate that I live in, and with three black cars, it's almost impossible for me to do this myself.
Use Microfiber towels for taking wax off the vehicle.
Chris
P.S. All of my cars are Daily Drivers. None are "SHOW" cars. But when freshly detailed look NEW even after many years of service.