Things you will need:

One can of Chaos black spray paint
One bottle of Chaos black paint
One bottle of Boltgun metal paint
One bottle of chainmail silver paint
One bottle of Mithril silver paint
One bottle of Goblin green paint
One bottle of scorpion green paint
One bottle of either Shining gold or Burnished gold paint
One bottle of Snot green paint
A fine detail paintbrush



Step one:
Always remember to put in the transparent green rod AFTER you are done glueing and painting.

Step two:
First, undercoat your model with a spray of Chaos black.

Step three:
Now go through with your brush and Chaos black. Make sure there is no grey on your model.

Step four:
Next do a complete drybrushing of Boltgun metal.

Step five:
Then paint all of the model (except the chest symbol and gun)with a mix of Boltgun metal and Chainmail silver.

Step six:
Next do a complete drybrushing(except the chest symbol)of Mithril silver.

Step seven:
Then paint the inner part of the gun Scorpion green.

Step eight:
Now paint the cable on the gun Goblin green.

Step nine:
Then paint the chest symbol with either Shining gold or Burnished gold. I personally think that Shining gold is to watery.

Step ten:
Now carefully paint the eyes with a dab of Snot green.

Step eleven:
Now let it dry and then enjoy the "fruits of your labor"!

At the very top is an example with some extra add-ons: