Hello All !
First of all, i would like to apologize not thanking you more quickly and wainting so long but I had to deal with some private matters. Concerning the technique, this is the simpliest, the cheapest and the more intuitiv one I know. Your coart of silver must be dry and well polished. After that, two or three layers of well diluated Gunze green colors are coming until you get more or less a good deepth. Dont let the paint dry completely. Start the chipping process with a good rubber by applying it and removing it nervously. You'll see the chipping appear. When the whole job is done, you can continue with some more fine and precise scratches with a simple needle to give more sharpness. I never varnish my model by the way. Dont like at all any kind of these finishes.
That's it !!!!