I wanted to a step-by-step on simple weathering but my phone crashed and I lost the pictures. You'll have to make due with this finished product.
The basics to dusty or dirty armor are this. Very light drybrush of Scorched Brown but only where mud would collect. Follow that with a drybrush of Graveyard Earth. that simulates dust and grime very well. If you need to brighten things up you can apply a very very light drybrush of bleached Bone. Be careful as going crazy with step can make things look strange. If you overdo it, you can back things up with a drybrush of Graveyard Earth again.
As far as the casualties, you'll have to saw or dremel off much of the back. A belt sander or disc sander works well for making the back flat. If this fails you can always cut a silhouette of the mini into the base and sink the mini into the base. Either way you get the same result.
For the lost accessories, make sure you do not just glue them to the base. When you drop something heavy on sand or mud, it rarely will land flat especially if it is heavy. Flatness muddles the effect of a soldier that has dropped his arms. Glue a small bit of sprue to the weapon and file it down. This will put the bit at an angle.
|This was the picture that inspired this.|