Great work! My first time using an airbrush was also on a Fett helmet, pretty daunting but once you get through it you can handle anything.
One spot that jumped out at me is below the front triangles and under the killstripes:
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Looks to me like some green paint peeled off when they masked off the visor area and killstripes and they hastily covered up it up. I used the airbrush but you could also thin some paint and do it with a paintbrush.
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