You will need the following

Tin bitz
Boltgun metal
Vermin brown
Drybrush
An old brush for stippling
Step 1
Basecoat the area's you want metal with tin bitz

Step 2
Drybrush said areas with boltgun metal

Step 3
This is where that old brush comes in handy*warning DO NOT use your best brush for this part* you need to get your vermin brown and dip your old brush in now on some toilet/kithen roll stiple your brush till hardly any paint comes off onto the towelling.Then stiple all the metal areas with it so that tehy get a coating of the brown

you will need for this bit
Old brush for stippling
Fine detail brush
Orange paint
Ogryn flesh
Step 4
Get some orange paint in my case i mixed up yellow and red and dip your brush in and stipple it onto soe towleing and go over the whole metal area again but really lightly

Step 5
Now you need your detail brush and ogryn flesh load your brush with the wash and go over the riviets any panels