Based on RS's suggestions, I'm doing the method of masking off the silver and painting the other colours around it. I'll get some photos up soon before I start on the mandibles, it's working pretty well so far. Great thing about acrylics is that if your masking isn't perfect, it's easy to fix up with a toothpick. If you scratch away too much, also easy to paint over and it doesn't show up after scotchbriting/black washing.