You can use gold foil and/or extremely thin gold wire and do 'Damascening' work on new or old engraving work to accent the background,lettering or make figures and patterns.
The foil sheet gold used is only a few .000 thick and is usually made by the artist by simply hammering thicker sheet gold out to the desired thickness. 24k and even 22k are very ductile and can be hammered down to a couple .000 thickness quite easily.
Silver is also used in some work along with other semi precious metals.
The base metal is prepared by making criss-cross cuts in 3 directions with a tiny chisel to throw burrs upwards. Those burrs are what the soft gold impales itself on when lightly hammered or burnished onto the surface.
Large areas can be covered with the foil,, like background. Lines and borders can be laid down with the very thin wire . It takes skill to keep lines and curves correct.
The Spanish were and are famous for this style of embellishment of steel but it is used by many.
The simple technique of the criss-cross burr structure to snag the gold is used by many engravers to inlay gold figures.
I've used it for many years in gold and silver inlays within the figures outline adding a shallow dovetail at the border. Then using nothing more than annealed gold wire of different diameters, they are set into the surface w/a punch. They stay put if done right and can be either flush or raised inlays depending on your preference.
No, it's not as simple as wiping gold paint into the engraving or lettering, but it's a true art form of metal embellishment that goes back centuries in it's practice around the world.