How to add battle damage to a Conquest, or how I learned to love foam

I spent some time last night on my Khador Conquest. I've moved to the stage where the model needs to be "damaged" up, to show all of the battlefield scrapes that the constant wars of the Iron Kingdoms would cause.  I imagine that as a valuable resource such as the Conquest would be, it would see a lot of front line use, and therefore it needs a very "used" look to it.  I am applying the same methods I used on some Super Heavy tanks I painted earlier this year, using methods learned in the Forgeworld Book, Imperial Armour Masterclass: Book One. 

The idea behind this method it is to add a lot of scratches with a gray color to show the Conquest's paint has been scratched down to the primer.  After that is completed, I'll highlight the scratches with a bright metal color to show that some of the scratches went down to the bare metal.

This is where the model started the evening.  Nice and clean, but not very realistic for something that spends it's time crushing the enemies of the Empress. . 

 My tool, a piece of pluck foam that has been torn at an angle so that it makes random paint "dabs".  I then dip it in Adeptus Battlegray, to represent paint that has chipped down to primer.

 Here is an unspoiled shoulder.

 Here is the same shoulder after being "damaged". 

 After the whole model has been "damaged".

 The back side of the model.  I also used a metal paint with the same method to "ding up" the black parts of the model.

 After the "scratches" have been added, I started to go through and some highlights with a bright metal color, in this case GW Mithril Silver to show paint that has been scratched beyond the primer level and down to bare metal.  I only finished this side, as it is very tedious, it took a long time to get even this far along.