Ok, my metallics are quite unorthodox and might sound a bit complicated, but I try to explain as best as I can
The entire process consists of the following stages, which I'll explain later on:
1.Basing
2. Shading
3. Applying shadows
4. Rehighlighting
5. Glazing
1.For the base I always use Vellejo ALCOHOLIC metallic paints. They are very adherent, so you just need 1 layer of paint and have a brighter shine. For this piece I used Liquid Silver for base.
2. For shading I use transparent paints from Vallejo Model Color range. They are similar to inks, but I prefer them much more. My shades are always very diluted and consists of several colors each. Also, I ALWAYS ADD Matt Medium to the mix, otherwise they will be to brilliant. I apply several (from 3-10) shades of each mix. They need to be carefully placed, so that the paint won't bloat. To shorten the process of drying I use hairdryer

First mix: Smoke+Woodgrain+Natural Wood+Sepia (a kind of orange-brown mix)
Second mix:Smoke+Purple ink
Third mix:Smoke+Green ink+Blue ink
3.For shadows I use Smoke+Black ink+Matt Medium. The mix isn't too diluted. I just add a lot of Matt Medium. It is faster that way.
4. For rehighlighting I use a mix of Metal Medium+Smoke, but you can use any metallic paints. Final highlights are placed with Liquid Silver
5. Glazes are placed to add more tones to the metal and smooth the transitions between light and dark parts by adding midtones. They are much less diluted than shades and includes more Matt Medium. I used:
First mix: Natural Wood (light yellow for brightest parts)
Second mix: Woodgrain (intensive red-brown for medium parts)
Third mix: Purple ink (for medium parts)
Fourth mix: Green ink (for medium parts)
Fifth mix: Smoke (for medium and dark parts if the metals became too colorfull)
The last step is too apply several layers of matt varnish, which will reduce unnecessary briliance and add more texture.
Ok, that's it

I hope it will help you. If you've got any further questions, dont hesitate to ask!