All paints are GW Citadel Colours.

Before painting, I spray white primer even over the figure, followed by a light spray of Gunze Limited Mr. Super Clear, which is a matt varnish.  I find this improves the binding of colour to the primer later.

When the primer layer is dry, I mask of the edges of the base, followed by filling the hollow plastic slotta base with epoxy putty (ie Milliput/Kneadatite).  I try to position the putty to compensate for any unbalance in the centre of gravity of the model.

I've chosen for this article a Warhammer Fantasy Chaos Sorceror, mainly because it's fairly easy to obtain anywhere.  Because the model comes in three parts (the whole right arm, the main body and the left hand), I temporarily assemble the model with a bit of Super Glue, drilling and pinning the various parts with a pin vice and brass wire.  The right arm is not stock, it's swapped in from another model (it was missing from the blister!

After the primer dries, if there's any exposed metal, I brush on some Smelly Primer to cover it up.  It's the same shade white, so there's no visible difference.

  2-2 Layering

I painted the helmet using the Near Metal Metallic (NMM) style.  The transition is Chaos Black->Shadow Grey -> Space Wolves Grey.  First, I mixed 1 part Shadow Grey to Chaos Black for the base coat, thinning the overall mix by a roughly equal volume of water.  At this stage, any mistakes are easily corrected by immediately daubing with water, there's no real damage done since we've just begun.

Next we add a bit more Shadow Grey, just dipping about 1/3 of the brush's bristles in, then dipping it into the diluted Shadow Grey/Chaos Black mix, gradually painting on highlights until the lightest point in the middle of the helmet.  The compound mixture is regularly diluted with a drop or two of water, since it'll be drying on your palette while you're doing this. The trick to smooth layering is to always make sure that the colour mix is dilute enough.  There are 4 layers here, with the darkest being Shadow Grey only.  Finally the last highlight is added with Space Wolves Grey mixed with a bit of white, carefully painted down the centre of the helmet. 

I do the horns next, starting with a black foundation.  Next is the first highlight of Black + Bestial Brown + Rotting Flesh, gradually lightening up the layers by mixing in more Rotting Flesh.  There are fewer layers here to create a greater contrast on the sharp edges of the spikes and ridges of the horns.  

The mask was painted with Snakebite Leather (and conveniently covering up any accidental paint).  From a base of Snakebite Leather + Leprous Brown, small amounts of Badmoon Yellow were added.  Next a layer of Leprous Brown + Badmoon Yellow was applied with a final layer of Badmoon Yellow + White for the hard edges and raised areas.