A: Industrially, it can be done in several ways. One is to use vapor deposition to coat an object with a thin metallic layer. Often, this can be enough to achieve the effect wanted, or it can serve as the conductive layer for electroplating. Or one can coat an object with the same materials used to coat glass to make mirrors. Some of these processes use several sequential chemical dips which result in a precipitated coating, others are simply a conductive paint or lacquer.

The old traditional way to do it would be to make the surface sticky, either with shellac, lacquer or wax, and then dip the object in powdered graphite, leaving a conductive graphite layer. A lot of baby shoes were bronzed that way. (This doesn’t work very well with modern baby shoes, which use rubber and lots of cloth padding.)

The simplest method used now is to make use of conductive lacquers. The best, and most expensive of these use silver powder as the conductive agent, but such paints are also made with copper and perhaps aluminum as well. You can find the silver paints not only through industrial plating suppliers, but in smaller quantities, from electronics suppliers as well. They use it to repair or modify circuit board traces.

Dalmar Co, which sells plating and electroforming supplies to jewelers and hobbyists sells such a paint, which I think is the cheaper copper powder based one. It works well enough, though the paint goes on slightly thicker than the silver ones I’ve used, and you lose a little detail. But you’re plating over it anyway.