This is a very open ended request. The
safest way is a Non-abrasive Gloss Agent.
Swirls are fine scratches are usually created by using incorrect car washing techniques.
I do not know of an easy way to do a good job of removing swirls by hand.
To quote "
You can not do by hand what you can accomplish with a machine."
To accomplish swirl removal from a vehicle "with black paint" I recommend a Dual Action (DA) polisher.
I'm not sure what brand/make and models are available to you in Pakistan. DA's Oscillate and rotate.
If you are looking for (or hoping for) a "magic sauce" that you can wipe on by hand and the swirls are gone...
It does not exist! That would truly be be amazing and lots of folks would be in line to get that "magic sauce".
At minimum it takes a Dual Action machine, pads (foam and/or microfiber), compounds, polishes and a learned process.
It also, takes knowing what type of paint you are working on. What year/make/model is the car? Is the paint hard or soft?
Essence Plus has recently come on the market and it helps eliminate swirls but it still requires a DA, pads, product and process.
Do you have pictures of the paint damage and a little more information? Extent of damage etc.? Tell us more. Pictures would help.