True inletting in silver and gold requires "dovetailing" the steel to provide an anchorage for the softer precious metal. As jaguarxk120, mentioned, just filling the existing with metallic paint can be done by anyone. It's a cheap way to try to up-grade your gun and usually the results look cheap. However, there are some models that had gold paint from the factory, and
paint sticks can be used to touch them up.
If you want something original, have your stock finisher inlet a gold medallion in your stock that has your monogram engraved. Here's a pic showing part of one on a custom stocked Perazzi:
