Doll base used in this tutorial is by Dollicious (site closed)

1) Start with your outfit - doesn't matter if it's fancy schmancy or ultra casual. Pencil in the outline and fill it with colour.
Note: gold/silver trim looks better on deep, dark colours (or black).
Click here for a close-up view
2) Create a new layer and start drawing your metallic trim. Use a medium to light grey for silver, or a bright, saturated yellow for gold. Stripes are simple, but patterns can really add some snazz.
I realize the trim on this particular dress looks a bit ridiculous, but this is for demonstration purposes only! :)
Click
here for a close-up view
3) Go back to your dress layer and make a copy for shading. You'll probably want to turn off/hide your trim layer to make shading easier. Shade the dress as you normally would.

4)
Go back to your trim layer. Make a copy of the trim layer for shading. To shade
yellow and grey for metallic effect, remember these two things:
- follow the shading on the dress
- shade the two horizontal edges of trim to give the trim some "bend"
If using tools, use the burn tool, at "highlights" at 10-12% opacity for shadows and use the dodge tool at "midtones" or "highlights" at ~6-8% opacity for gleam.
Note: if you want a very gradual or "dull" shine, then use a wider dodge brush with a lower opacity or skip highlighting altogether.


Example 1: Compare the left and right wrist trims. Note how shading the edges of the horizontal lines gives "bend" to the one on the right.

Example 2: Use different sized brushes and opacities for varying metallic effects - from dull (the neckline) to super shiny (the waist).

Example 3: Note
how the highlights and shadows of the trim follow the shading of the dress.
Here's the most recent doll I've made using this method.
Base: ApplePixelBox (site closed)