The technique I showed you is called Non-Metalic Metalics, used in miniture painting to get a realistic metal look without using metalic paints (which are, simply, Paints with metal flakes in them). If you have any questions, Just look it up! you'll find plenty of tutorials, just mentally change out water blending with gaussian blur plugin and Model with drawing.
How you can recreate it in your work:
1. seperate your metalics from your fabrics/flesh/wood in your painting in it's own specific layer. If you colored in cells this should be pretty easy.
2. Make 5 blank layers above your gold. I personally making the rest transparent for now, but that's up to you. Label them something like 'shadows/deep shadows/Highlights/bright works/ambiant light' or anything to that effect.
3. On the 'shadows' Layer, pick a nice sized brush and go over where the light would recess on the armor (like the grooves behind ridges that block the light) with a deep Terracotta/Red Clay color.
4. On the 'Deep Shadows' Layer, take a finer brush and go over the spaces again, further or less touched by the light with a darker, more mulched brown color (think dark chocolate).
5. use the Gaussian blur tool, and individually blur the Shadow and Deep Shadow layers. choose the blur to fit the color blend, but don't worry if it blurs into area you don't want them, you should need to touch it up anyway. Typically, the Deep Shadows doesn't have to be blurred as much, while the Shadows may need to be blurred a fair bit to look right. Once done, you may have to touch them up so the colors don't bleed into areas that are supposed to rise up, or off the armor completely.
6. the armor should start taking shape now. Now it's times for highlights. Where the light touches the armor strongest needs to be brightened to a nice pastal yellow on the 'Highlights' Layer.
7. Just like with 'Deep Shadows', Bright Work needs some luvin' too! Touch up the very top of the ridges with an off white color (like a sun bleached bone).
8. Again blur to your liking and fix up as with step 5.
9. Now, for Ambiant light. All surfaces reflect light just like a mirror will. It's just not as strong. Shiney surfaces, like gold, show this effect the strongest and require a touch of strong Ambiant light. This is just like Bright Work, but reflecting the exact opposite way of the main source of light. this will have to be blurred, but just slightly. the more you blur it, the more it will throw off the mind's eye in understanding what was intended to be the main source of light.
10. Your armor should look nice and sparkling. I would personally suggest taking the primary color layer and making a copy, putting it higher then all the other layers, and playing with, overlay, multiply, lighten, darken, screen, etc, and most importantly, the opacity. Those colors, most likely are not linear to each other, but by having a layer of one color over them with at 10% opacity, It will draw them together. you can also experiment with noise and and a whole slew of other filters to experiment with the finish of the armor.
Side Notes:
The stronger the difference between the shading and the highlights, the object appears to have a stronger gleem or luster to it.
The more area the highlights take up opposed to the shaded areas, the brighter the source of light appears to be.
The darker the shadows, the closer the light source appears to be.
The more area the shaded areas take up, the dimmer your light source appears to be.
If you have trouble deciding how you want it shaded, try finding a refrence picture and adjusting the curves so it suits your color scheme. Don't just eye dropper the color(you want to learn how to do pick colors yourself!)!