Scale effect is not just adding white paint to your black paint, the best demonstration of scale effect we have is with tanks and AFVs models. Imagine the models painted a single color, they would not look so convincing, your goal when applying scale effect must be to add some depth and highlights to your models. Black is, of course, a special color, you must add some blue or brown to it with the white paint, to highlight the hull, but, of course, some parts of the hull must still be black.
I paint some figures too, but, to have a good scale effect, on a face, some parts of the face must be almost white, and some parts must be almost black, otherwise your model would not be convincing.
It is true, that we do not see often scale effect on model ships, but, carefully applied, it would be a bonus for your model.
Take a look at my icon, Nelson's face and hat, you see his black hat is not all black.
Michel