The armour is done using a quite simple technique: a highly diluted raw sienna oil wash over gloss-warnished white, sealed with matt warnish afterwards. Golden parts are done the same way - just black oil wash over vallejo mc bronze. Hope this helps!
This Dreadnought is stunning!
The rusted metallics really suits the Death Guard, and you've done a great job on the off white armour.
Would you mind sharing how you painted the armour and the gold? :)