- Prime with a silver like   Steelforge Silver  , then coat Chopper and the destroyed droid on the base with Vallejo Environment FX Rust Texture. 
- Heavily drybrush the main chassis with   Celestra Grey  , and the head unit with   Squig Orange  . Use a stippling motion - want most of it covered. 
- Boost the chassis a bit with a lighter drybrush of   Wrack White  or similar light grey, and do the same with the head unit via some bright orange (I used   Troll Slayer Orange  , then added a touch of   Screaming Skull  for the very top highlights)
- Using   Yriel Yellow  , I picked out the 'stripes' that separate the head and chassis using a stippling motion to imply wear/tear. 
- I picked out a few panels with   Vulkan Green  and heavily thinned   Black  . Using a less-thinned black, I blocked out the top antenna and the two arms. 
- Drybrush the base droid with   Necron Compound  
- I then did a simple grey basing scheme, which I'll use for each of the SW Rebels' Ghost Crew. Vallejo Dark Earth Texture Paste, washed with   Basilicanum Grey  , then drybrushed with   Stormvermin Fur   and   Administratum Grey  . I wanted to do the base at this point so the smoke/explosion below Chopper was easier to imply with some basic OSL/etc. 
- I used a weathering pencil (AK Dust/Rainmarks) to add some chipping/wear to the 'arms' 
- Basecoat the thruster burst with   Matt White  , coat in   Baal Red  , then wet blend the outer parts black to light grey
- I stabbed some Vallejo rust pigments into the base, and sealed with alcohol, then rimmed with   Corvus Black