If you want the same whitish pearl sheen the enterprise A had in the movie then I recommend GOLDEN FLUID ACRYLIC iridescent Pearl {Fine}. When doing my 350 Enterprise I tested a dozen differant sheens and colors and that gives the closest match to the film finish. And it still showed through the decals.
I used a white primer as the paint is quite translucent. gray primer would really darken it too much.
You can get them at art supply places or google Golden and you'll find them.