Paint finishes on models are immediately a problem once metallics come into the equation. Coloured metallics I have not quite figured out, but for silver, I have a recommendation.
The oft maligned Humbrol do an aluminium paint no.27002. This is one of their 'Metalcote' colours. I have tried the 'steel' from the range, it works. When buffed up it looks just like bare steel. The aluminium simply does not do this, but is excellent as a 'scale' silver paint.
I used this with an airbrush, thinned with their own ENAMEL thinners and it worked a treat. The next stage will be a coat of silver on a body, with a coat of enamel paint/laquer mix to see how it comes out. Just like prototype polychromatic stuff, but I think gold was the preferred base coat.