[Karin Wells]

When you have a completed raw umber + white underpainting, the next step is to add glazes and scumbles.

In making something look like gold, use transparent glazes like raw sienna and raw umber overall to get the dark gold look underneath and in the shadows.

Then you use opaque color on top of the wet glazes and scumbles - like Naples Yellow + whatever to represent the shiny gold areas.

It is all a version of the directions you already quoted.

Remember that oil paint - even what we call "opaque" - really isn't. It is translucent and the underpainting layer will show through the top most layers to make those beautiful and subtle halftones that the old master paintings have.