I have experimented with several chrome paints. In every sing test, applying clearcoat over the chrome dulls it. This is a universal problem. You can't clearcoat chrome paint if you need the best shine possible.

As for chrome paints, I have had the best results with SMS Hyperchrome, and Green Stuff World Chrome paints.

The SMS Hyperchrome can be applied over any color, the only thing it needs is a high gloss surface. So I don't even paint parts when using it.  I apply some primer, then I clearcoat it, and then apply the SMS Hyperchrome.  Sometimes I even skip the primer and just clearcoat the plastic parts.

Apply SMS Hyperchrome in 3 or 4 very light dust coats. It will look hazy but this is ok.  Let it sit a few hours and then take a soft cloth and buff off the haze and it shines right up.

You can handle the parts a little bit. If you handle the parts repeatedly you will eventually dull the finish, but it take a lot of handling.