Liver of sulphur.... use it fairly cool and don't preheat the piece.
Either dip or paint on the LOS and as soon as the color begins to
approach the gold color you want (that's the first color in the
spectrum that develops), immerse the piece in COLD water and scrub
thoroughly with soap and water. Leave it immersed for a few minutes
and scrub again (I use a toothbrush and my hands, not a brass brush
which would remove the patina).
The piece shown here has more variation in tone than you're looking
for... I've got another piece that has a gorgeous even gold tone all
over but don't have a photo handy. If you look at the top area of
this piece, you'll see the color I'm talking about:
If the process goes too far, hit it with a torch and the patina will
burn right off,... pickle and clean and you can start over again.