Black cars are super difficult to handle. Even my white car gets super dirty super fast.
However, wax does keep the dirt at bay though never dry dust the car. Look into ECH20 Waterless Wash. That takes a BIT more time compared to dry dusting but is a good solution to avoid swirls and spider webs on a black car.
Also, worth noting, black cars are the MOST DIFFICULT to maintain and to avoid scratches and swirl, so even when you do the basic stuff right, you'll still get them. It's just a matter of sooner vs later.
Heck, I did all the care for my White Grande to avoid all kind of scratches then saw a nashai dry dusting it when I was in the restaurant. I chased him off but I laughed inside k car care or microfiber waterless kya kya ni kr liya only to end up having a nashai dry dust it out of nowhere 
Also, I was in Lahore and in the parkings, I got 2 scratches on the bumpers in just 1 month in Lahore. Pata nahi Lahore walay kya krty hain but you can't avoid this stuff so the very first thing is to be mentally at peace with your car. And then care for it as much as you easily can and would like to. No need to be super obsessive or anything.
