Hi Carlos!
I have been modelling since the early '50's and using metallic finishes for about 20 years. I started with "Rub'n'Buff", that's how far back I go! The all-time, far and away, none better, is the line of Alclad II metallizers. They are a bit more expensive than some others, but for durability, variety of shade and reflectivity, ease of application and no decaling problems, the stuff is totally in a class by itself. Try it next model, I think you will be pleased. And the stuff has good shelf life. I just add laquer thinner (it evaporates) and a bottle of Alclad I,10 years old, is again serviceable.
Tony Ryan