A general guide on the corroded Steel decorating my personal Death Guard
  - Basecoat   Iron Warriors  
 - OPTIONAL: Wash with   Nuln Oil  
 - Dab corroded areas with   Seraphim Sepia  followed by a dab of   Agrax Earthshade  in the middle of the   Seraphim Sepia  
 - Put a small amount of   Typhus Corrosion  in the agrax for texture
 - With an old brush, dab a little bit of   Ryza Rust  on top of   Typhus Corrosion  
 - Highlighy edges and scratches with   Ironbreaker