Black is not for everyone
e46 Supra and SteveL are closest to having it right.
Having swirls on black paint is "not just the way it goes." Black will simply show more vividly whether you have good washing/waxing techniques.
Products have little to do with getting scratches or swirls -- with some notabile exceptions.
Most wash mitts you buy at auto parts stores are not truly all-cotton even though they say they are (I have called the mgfrs., and they admitted there was poly binding in the frabric. Poly WILL scratch the paint.
Other than that, scratches are caused by rubbing the dirt across the paint (most dust is microscopic rocks!). Wash with two buckets -- one with clean, soapy water, the other filled with clean water. Using a nozzle-less hose, always run water over the area you are washing. When you have done a panel, shake/rinse the mitt in the clear water and then recharge it in the soapy water to start the next panel. Wash in a protected area (I wash my car IN the garage) and dry using either truly all-cotton towels (with the poly binding cut off) or the new mirofiber towels.
Water blades DO NOT scratch you car -- what scratches your car is any left-over or new dirt/dust on your car as you are drying. If you are not confident you can get your car that clean, then use a towel instead.
I also always wash/dry/wax in a single direction so if I do get a swirl, it is less likely the sunlight will catch a reflective edge.
Zaino is a HIGHLY reflective polymer coating that tends to fill some of the scratches. Personally, I think it is the wrong product to use over black since you want the deep, wet look that black best shows, not a mirror-like finish, but to each their own.
Hope that helps.