I have used this product. First things first, it is not the miracle product that it is being sold as. However, it still is better than leaving a bare chip exposed and making the touch-up a lot less obvious.
It might take you some amount of practice to get it right. The nice thing is if you rub too much, you will just end up right where you started. A bare chip mark. From there, you start the process over again.
My biggest problem at the start was not knowing when to stop rubbing. I found that putting two pieces of tape parallel to each other on both sides of the chip helps a lot. I wrap the plactic card with the cloth and apply langka onto it. When I rub, I apply pressure on the part of the card that rests on tape and not on the chip mark itself. From there I rub back and forth in the direction of the tape. The tape acts as rails and raises the contact point. Thus preventing you from rubbing out too much of the touch-up paint.
Another thing I learned is to use a little bit of the solution at a time and use a new spot on the cloth after a few swipes. Reason being, after a couple of swipes, you will see that the cloth will get dirtied-up. If you continue using this same spot on the cloth, some of that discoloration will transfer back to the chip. Embedding itself on the borders and ridges of the chip. When it dries up, the chip may look a little darker than what you want. Thus more noticeable. For me it does cause I have a light colored car.
Just remember, this is not the complete answer for dealing with paint chips. It only makes it a lot less noticeable. Hope this helps.