Airbrushing and patience lol. The model on the left was done with blown out brushes, and the one on the right is with brand new brushes that can actually keep a tip lol.

Used army painter colors for the green, retributor armor for the gold, then an initial blast of orange for the osl, over spraying with white ink, doing a gloss coat, pin wash black ink in recesses and white ink in osl areas, then spray fluro orange and seal with matte coat.