how to maintain a black car??

A black or dark colored vehicle is perhaps the most high maintenance when it comes to detailing. Perhaps the best way to minimize swirls is to use a buffer a DA (Dual Action) buffer. Remember the saying "Having the right tools is half the job" the same is true in washing and maintaining a spotless vehicle.

I use the following:

Dual Action Buffer (I use one made by Porter Cable)
Foam Pads
Swirl remover 2.0 #9 (I use this every other time I detail)
Meguiars show car glaze #7 (polish)
Meguiars Hi-tech yellow wax #26

* After the car has been carefully washed and dried (use a chamois) apply a light non abrasive polish/cleaner with a foam pad or a very fine terry cloth. Application can be done by hand or a buffer I personally use a dual action(DA) buffer and this is perhaps the best way to minimize swirls and its a lot less labor intense

*True polish does not need to dry to a haze like wax so after spreading the polish evenly on the surfaces wipe off excess. On cars that have a clear coat you'll begin to notice a shining glaze as you wipe away the polish on older cars or cars that don't have a clear coat layer it will take more polish to bring out the shine.

*Wax, a lot of consumers mistaken wax as polish and vice versa. The truth is that wax is a protectant it protects the paint against UV rays and the polish from washing away. Rule of thumb, polish shines and wax protects.

*Applying wax should always be by hand with a foam pad. Use a carnuba wax and apply evenly (exactly like applying polish). After application wait approx 15-20 minutes until the wax has a hazing appearance and wipe off excess with a ultra fine polish cloth. This is necessary because any other type of cloth is abrasive enough to create more swirls as you're removing the wax.

This is just detailing a dark vehicle in a nutshell if you have questions feel free to ask.