Cut out the shape and give the whole surface a light sand with fine sanding block or paper.

Spray the shape with a metallic spray paint

I used Silver Wheels Pro

After the silver is dry cover the shape with black acrylic paint making sure you get into all the etched details with the paint 

with a moist cloth wipe off the acrylic paint leaving the engraved areas filled 

this process can be repeated until you get the desired look