Gun servitor - mega tutorial with airbrushing and weathering tips!

You asked for a tutorial for the weathered mettalics but I though a full, all bells and whistles, mega tutorial would be better! I tried to cover each and every part of the mini and also went into some detail on airbrushing and weathering techniques. I hope you'll enjoy it!

Weathered steel

For this I used the 'Eavy Metal tutorial from UK WD  369 which I've adapted slightly. One thing to keep in mind is that the first washes should be aplied more liberally while the darker washes should be focused on the recesses and shaded areas.
- Basecoat with Boltgun Metal
- Shade recesses and joints with Chaos Black
- Wash with Gryohone Sepia
- Wash with Ogryn Flesh and give the recesses some extra treatment
- The recesses are washed with Devlan Mud
- Patches of Thraka Green are aplied with special attention given to the recesses
- Highlight with Chainmail
- Highlight with Mithril Silver

Clean steel

- Basecoat with Boltgun Metal
- Highlight with Chainmail
- Wash with a 2:2:1 mix of Devlan Mud: Badab Black: Leviathan Purple
- Highlight with Chainmail
- Highlight with Mithril Silver

Gold

- Basecoat with Tin Bitz
- Paint everything except deep recesses with Dwarf Bronze
- Highlight with Shining Gold
- Wash with a 2:2:1 mix of Devlan Mud: Ogryn Flesh: Leviathan Purple
- Highlight with Shining Gold
- Highlight with a 1:1 mix of Shining Gold & Mithril Silver

Skull

- Basecoat with Calthan Brown
- Paint everything except deep recesses with Dheneb Stone
- Wash with Devlan Mud
- Highlight with Bleached Bone
- Highlight with Skull white

Plasma cannon casing

- Basecoat with Khemri Brown
- Wash with Devlan Mud
- Highlight with Graveyard Earth
- Highlight with a 1:1 mix of Graveyard Earth & Kommando Khaki
- Highlight with Kommando Khaki

Green Cables

- Basecoat with a 1:1 mix of Orkhide Shade & Chaos Black
- Highlight with Dark Angels Green
- Wash with Devlan Mud
- Highlight with Dark Angels Green
- Highlight with a 1:1 mix of Dark Angels Green & Snot Green
- Highlight with Snot Green
- Highlight with a 1:1 mix of Snot Green & Bleached Bone

Red Cables

- Basecoat with a 1:1 mix of Mechrite Red & Chaos Black
- Highlight with Red Gore
- Wash with Devlan Mud
- Highlight with Red Gore
- Highlight with a 1:1 mix of Red Gore & Blood Red
- Highlight with Blood Red
- Highlight with a 1:1 mix of  Blood Red & Dwarf Flesh

Tracks

- A basecoat of Chaos Black was applied
- The tracks were heavily drybrushed, first with Tin Bitz and then with Boltgun Metal
- The area where the tracks meet the body of the tank was washed liberally with Devlan Mud
- A wash of thinned Vermin Brown was applied liberally all over the tracks. I used a piece of kitchen paper to remove excess wash leaving the wash only in the recesses.
- A final light drybrush of Boltgun mettal was applied

Tank parts

The part of the mini that was essentialy a miniature tank was mostly painted using an airbrush and since not everybody is familiar with airbrushing I'll cover this part in greater detail.

First a basic paintjob was applied.
- A basecoat of Codex Grey was sprayed at a pressure of 10 -15 psi taking care to leave the recesses darker.
- Scorched brown was sprayed at a pressure of 5- 10 psi to shade the recesses.
- Pannels were highlight with a 1:1 mix of  Codex Grey & Fortress Grey (The pressure is set again to around 10 - 15 psi for this and the next stages of the basic paintjob).
- A final highlight of Fortress Grey was sprayed concentrating on the centre of pannels.
- Fortress grey was drybrushed in the mini to highlight the pannel edges.

Then I applied some battle damage.
- First Charadon Ganite was sponged on, concentrating on the edges of pannels and places were wear and tear will be greater. For this I used the foam tham comes with a blister pack, dipping it in paint and them whipping most of it a way. Sponging was then dome witha stabbing motion on the mini. It's best to test on a piece of scrap (or on the underside of a tank) first to get the feel of it.
- Then Boltgun Metal was sponged on at areas where the bare metal would be exposed.
- Using my finger I applied some graphite (which I had scraped off a pencil) to edges and areas where bare metal would be exposed to give an extra mettalic sheen.
- Watered down Vermin Brown and sometimes also Blazing Orange was applied around rivets to simulate rust. The intensity of the washes varied in order to portray different stages of rust. It's better to apply several thin washes instead of a thicker one.
 
Finally the mini was weathered.
- Graveyard Earth was sprayed at a pressure of 5- 10 psi at the lower part of the mini to simulate dust.
- A 1:1 mix of Chaos Black & Scorched Brown and then pure Chaos Black was sprayed at a pressure of 5- 10 psi to simulate soot around the two exhaust vents.

And since all this airbrush talk can drive a person crazy it's time to give you some airbrush tips.
- Window cleaning fluid makes a great thinner for airbrushing GW paints (though I haven't tried it yet with foundation paints or washes). Tamiya also produces a good thinner for acrylic paints but it's harder to get and more expensive than window cleaning fluid.
- It's always best to thin your paint a lot and go for multiple subtle layers of colour. It will also prevent nozzle clogging. I can't give you an exact thing ratio but for basecoating it is around 4:6 paint: thinner and for detail work such as weathering and shading it is around 2:8 paint: thinner. In general the lower the pressure you use the thinner your paint should be.