Step by step weathering Mega Zaku II shield

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Used a medium Tamiya file to rough up edges.  This is not necessary but I feel it gives depth when the light reflects of the metallic paint.
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Used a rotary tool to make bullet holes.  Making sure to make the holes bigger at the surface and smaller as they went in.  There is no need to go all the way through the plastic (the shadow will look deep enough)
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Use a lighter color paint then the color of the plastic to go around most damaged areas. 
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Used a silver color around the bullet holes.
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Used gunmetal inside all of the light green paint and in the inner part of the bullet holes.  I used a tooth pick to apply it.
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Next I used the brown real touch marker and smeared it with a Q tip. I do this around panel lines and chipped paint to represent rust.
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After that I do some really light dry brushing with gunmetal and some dots of real touch brown blended in with the q-tip.  If some chipped paint effects don’t look right I clean them up by chipping it away with a tooth pic.  Real touch marker can be cleaned up with a white eraser.  All of this can be cleaned off with rubbing alcohol.
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Update on Mega Zaku project

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Weathered the shoulder guard.
This was done on unpainted plastic.
This was done with a Gundam real touch brown marker, gunmetal paint, and a mix of paints to get a light green.
First I use file were I want some real rough damage (in this case along the outer edge).  Then I roughly put down the light green paint with a tooth pick where I want the chipped paint.  Then I put gunmetal paint on top of the light green paint trying to stay with in the green paint.  If it looks to smooth or you make a mistake you can chip the paint off with a tooth pic when it is dry.  I then used the real touch marker on all panel lines that rusty rain water would pour out of.  Also used it on the bottom edge of the chipped paint areas.  With the real touch I just use a q-tip to smear it downward.  Then I did a little dry brushing and a couple of dots from the marker her and there that are then faded in with the q-tip.  I will follow up with some step by step pictures. 
The effects look a little strong in the pictures but will loose some of the intensity once top coated.
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