What are the steps of a full decontamination wash, and in what order?

Work from the gentlest step to the strongest and rinse between each one. A typical order is: 1) rinse the car to remove loose dirt; 2) apply an alkaline pre-wash or snow foam to loosen traffic film, bugs and oily grime, then rinse; 3) contact wash with a pH-neutral shampoo using clean mitts; 4) use a bug and tar remover where needed; 5) apply an iron remover to dissolve iron fallout and brake dust, then rinse; 6) if water spots remain, use an acidic or coating-safe mineral remover; 7) clay only the areas that still feel rough. Finish with a final rinse, dry the car and inspect it before polishing or protecting. Never mix products or let them dry on the paint.