One of the first things I buy when I get a new car is touch up paint. I don’t wait for the first stone chip damage to happen before getting the paint as the inevitable stone chips will happen sooner or later, and I like to be prepared.
On my last two cars, I’ve used the Chipex kit. As
@kevster184 has said, it’s not perfect, but it does a pretty good job of hiding / disguising stone chip damage, and the beauty of the Chipex kit is that if you make a mistake or a poor touch up attempt, you can just remove the paint with the blending solution and start again. I’ve found it does take a little practice to get good results.
When I’ve used manufacturers touch up paint, I also don’t use the brush supplied - it’s far too big for most jobs and will just make a blobby mess. I either use a cocktail stick or use the end of an unfolded paper clip, as you can achieve much better precision in not applying too much paint and you can get the paint to go where you want it to. I’ve also used a cocktail stick with the Chipex kit on small stone chips.