A gloss coat could work, but it can sometimes magnify the "grain" in the metallic paint, especially on a "dull" silver colour.
I've found that adding a very small amount of gloss white to the silver, gives a good impression of "aluminium paint", and this can normally be gloss-coated, when dry, without magnifying the "grain".
Experiment first, to achieve the desired finish, as it doesn't take much white to "knock back" the silver.