The readily chromed parts contained into kits are unsuited for a scale model. Both if you are building a weathered car, but also for a new one. Unless you want a toy-like effect...
And cleaning up the parts removes the chrome paint too.
How to do ? For a scaled down chrome-effect paint TEWM10 Chrome, from the W Metal range directly on plastic, any color it has. Here I've airbrushed Chrome unthinned, at a pressure of ab.21 psi, alternating one pass of paint to one pass of just air, until achieving the evenly effect you see into the two pictures below, token with different lightings.
If you want a more sober effect, you can p.ex.paint a first coat of W Metal TEWM07 Iron, that is a darker semi-metallic tone.
Than paint a thin coat of Crome, without completely covering the underlying color. You also could try other W Metal tones as a basecoat, at your taste.
One nice feature of W Metal paints, compared to other and more known nitro-based paints, is that you can overlap different tones without affectiong the previous layers.