Gold toning has been used since the earliest days of photography as a permanising treatment, but as selenium toner is superior to it in this sense, nowadays because of the high price of the metal, gold toning as a teatment tends to be used more for its special tonal effects.
Tetenal Gold Toner is available as a 1 litre working strength solution. Prints are immersed in the single solution & agitated, it's best to do this under good lighting, & daylight will best show the tonal shifts. The action is slow, but bear in mind that's real gold in there, 0.5 of a gram, hence the high price. Capacity is also limited, maybe ten 9.5 x 12" prints, although this is influenced by print density; the lower in key the print, the more it will exhaust the toner. Care has also to be taken to avoid contaminating the toner, and it is best to use a new dish & keep it solely for gold toning use.
On a standard print, gold toner will substitute part of the silver image grain with metallic gold, which will be evident as a subtle blue colour. The intensity of this will depend on the silver particle size distribution in the print, and warm tone papers will usually in shift tone more than cold tone papers. Length of time in the toner also controls image colour. However if you are looking for a subtle metallic blue, moreso than from regular blue toning, a paper such as FOMA Variant, processed in Tetenal DOKUMOL, followed by gold toning should give an interesting result.
The other side to gold toning is the action on sulphide treated prints. On a previously sepia toned print, the brown image will will change to a unique red/brown image, and the qualities of this can be quite spectacular.