I found some small points of metallic paints at the back of a cupboard, so decided to see how they looked on some #10 horns rejected for bubbled tips. So these are metallics on black pigmented resin.

I should note, the orange-metallic poster paint is actually the RIGHT horn! The photo makes the gold seem more orange than it looks in person. In person the right-hand one looks very washed-out.
Did get a nice burnished look in general. May be better overlaid onto a different pigment though.

Thought folk would like to see the sort of effect you can get with metallic paint! In this case a Humbrol enamel and a unknown poster-paint.