Monkeybutt I know about your build, you have done a terrific job with both little beasts.
Anyway I thought I give you some tips about chipping the way I make them nowadays (ala Mig).
To start, you need a lighter shade ofthe model's base color, some very fine pointed brushes, a little water nearby a small piece of sponge, a steady hand and a lot of patience.
Firstly with the light shade of the base color the chips are painted in a random way.
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To achieve this try not to work on the same spot for more than a few seconds, and move around in a chaotic way, painting here and there building the effect gradualy in the surface that you are working. Avoid similar patterns while painting the chips and use the tip, the side and different movements of the brush to create variety. In case you are not satisfied apply some water in a brush and wash away the color while it's still fresh and repeat.
After that using a dark brown color and an extra fine brush repaint inside the chips made earlier simulating exposed metal. A sharp brush is absolutely required on this step.
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You can leave some chips on the lighter shade of the base color. This looks good on spots painted with the camo scheme.
Finally by using a sponge the chipping effect can be further enhanced on selected areas that receive heavy wear. The sponge can also be used on the whole surface but very very lightly.
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It's an easy method which can really add to a model. Give it a go!
P.A.