I can't help you out much with paint usage on those vinyl parts but to tone the chrome down and to give it a more true metal look I usually coat my parts with Tamiya Smoke. It works really good at reducing the toy like look from model chrome and levels out nice.
The paint is X-19 Tamiya Smoke.
To illustrate, the wheel on the R/H side has no Tamiya Smoke paint on it where the L/H was treated with a coat of it.