Well, I believe Cyril or someone else would probably be better suited to reply than me but here goes nothing...
It\'s just painted.
Now, in order to make it look like an engraving you\'ll need to highlight the parts where light would reflect - just as if there was a sharp edge just below the engraving.
Or that was what my girlfriend told me to do when she commented my stuff. Said that the engraving I painted didn\'t look like what it was supposed to be and suggested that I\'d make some highlights below the engraving. Isn\'t she helpful?
I\'d send you a pic as an example but I haven\'t got the minis here right now... Maybe this will help you some:
http://www.rackham-store.com/boutique_us/images_produits/GBRG_0502_1.jpg
If you look carefully, there\'s a very thin highlight just below the swirly pattern which makes it look like an engraving instead of something that\'s painted on the chopper.
I hope this makes some sense. It\'s 01:00am and this certainly isn\'t the best time to explain something in foreign language...