Yes Langka will work.
There are two issues with Langka.
One is metallic paint.
It will be no better than the touch up paint, and touch up paint is notorious for not having the same metallic content as your original paint.
The other is technique.
Along about your second or third scratch, you get pretty good with it. At least I did. So practice on another car can help. It helped me.
After I finished my Miata, which had a total of 5 or 6 areas of Chips and 1 scratch, the car won first place in the Ft Pierce FL Concours (Multiple coats of Zaino) in 2001 in it's class.
What Langka is:
It is a "system that allows you to touch up chips and scratches using techniques and materials that are similar to those used by a professional body man. However it is no good for dents. etc. It is just a Paint finishing system.
You can fail.
My first scratch (That I tried on my Chrysler), didn't look good at all. My daughter, OTOH did her first scratch like a pro. She is a good deal more "artistic" than I. But after I got the hang of it, (Patience being a key) I did well.
I have seen some jobs done with a heavy metallic paint that looked like crap. Because the touch up paint didn't match.
I like it.
I recommend it.
Homer