Gold can be overlayed in several different methods. Fusing is the technique used in Dublee. Fine silver is usually used with high karat gold.
A bimetal of gold and silver is available from some refiners and precious metal suppliers that uses diffusion to bond the two metals together.
It is also possible to attach the gold to the surface of sterling if you use the technique of damascening used in Japan and Spain and by some contemporary American artists. The gold is held to the silver by crosshatching the surface of the silver and carefully hammering the gold onto the surface allowing the gold to be held by the burrs created by the crosshatching.
Kumboo or Keu-boo is a Korean method of bonding 24k gold to the surface of fine silver or sterling with fine silver surface created by copper depleation. It is relatively easy to do and has been explained in a few modern books on Jewelry Techniques.