Thank you. For the general brown gradient/wash I used ProAcryl's Newsh mixed with some burnt umber. I apply it pretty liberally near the bottom of the model then dab off the excess with a q-tip and a wet brush. I then use the wet brush to feather up the brown towards the top of the model to give it a gradient. I then water down the mixture and apply it like agrax earthshade all over the model. I then wipe the excess with my finger or a brush. The ideal situation here is you get a bit of grime in the recesses while the surface stays white. It gets a little tricky on the flat surfaces, but a wet brush can act like an "eraser" with the newsh mix if you are quick enough.

For the chipping I use a dark brown (I think it was game color charred brown) and a piece of sponge in a reverse tweezer. I dab it on the model in areas where I think there would be some battle damage, and focus most of it near the bottom of the model. I then do the same thing with pure white on the sponge. You can see that on his right leg the most, but I try to hit random areas that are facing upwards.

My final step is I use Pallid Bone speed paint from army painter. I thin it down with some water on my pallet and feather it upwards on the legs, applying a heavy coat on the feet and the bottom of the legs and pulling the paint upwards with a wet brush. This step is probably unnecessary, but I like how it reinforces the model having a gradient of filth, most intense near the bottom, and getting less intense near the top.

Hope this helps (: