Those are very accurate observations about metallic paints used for scale models. I'm glad you are aware of that and doing something about it. This problem is also present in larger scale models (like 1:24 scale), and even model paint manufacturers seem not to be aware of it, producing paints for model hobbies with oversize metallic particles.
I have also noticed that quite a few metallic nail polishes are available where the metallic color is smooth, not having distinguishable reflective particles. Also some metallic paints from Alclad II also have very fine grain particles resulting in smooth metallic finish. Those then can be over-sprayed with transparent paints, resulting in more in-scale metallic colors.
