Thank you again guys.
I will share the basics of my technique, as it is just basic faux finish work, but there are some specifics about paint mixture that I won't divulge because they are my own concoction that I found did something really cool that regular acrylic paint doesn't.
The technique in this case begins with a polyurethane casting that has been cast from a mold which has been pre-painted with a bronze colour spray paint. A better quality paint will work best for this - I tried a cheap paint once and ended up with a bad casting. Once that is out, you have a pre-painted resin casting, but it is all one uniform colour; in this case bronze (some paints give a more gold like bronze, while others give a more brownish/goldish/greenish colour). But real bronze is not uniform in colour. So...
Bronze is mostly copper, with varying amounts of tin added. The copper gives it the gold-like colour, the tin gives it the dark somewhat blackish tones, and the patina from the copper can give it a green hue. In some cases the green can be very dramatic. In many cases the green is not overly apparent unless you look closely. I went for a casting that just had a hint of green - not really visible in the picture. The green I used to "age it" is a mixture of green and black (but this is where I made some "special modifications" to enhance certain features of the finished look).
This was carefully applied a little bit at a time, very watered down, with a soft brush. I did small areas, wiping away the paint from the high points, so the dark lay in the deep areas of the texture, with the original bronze colour showing through on the high points. The larger/deeper the creases, the more dark I added, lightly buffing it into the texture the whole time.
After that is done you end up with a somewhat aged looking surface, but it still doesn't have the "glow" you get from real bronze. So I took some Rub'N'buff gold and gently and carefully buffed that onto just the high points - the nose bridge, the forehead, the cheekbones, the edges of the collar, around either side of seams in fabric, etc... This must be done with very very little rub'n'buff at a time, or you end up with dirty great globs of gold on your surface that won't come off unless you use a solvent. I got a few spots on that were too thick and I had to use some alcohol to rub some off. The trick is to dab tiny bits of the stuff onto the cloth and then rub it on a styrofoam tray or something to get the most of it off before you start gently buffing it onto the casting. For the areas where there is more gold tones I did this over several stages of buffing, rather than try to get it all at once.
Anyway, them's the basics.