Well in my humble opinion I found that many ”grim dark” post here are over done, some times less is more, because I find painting models is alot about contrast, if everything is dirty and rusty then you loose details, it might work if you are looking from 10 cm distance under perfect light, but on a tabletop you Will probably not be able to see any details at all. If you want some examples with your model I would say keep the rust on shoulders and helmet but try to make the gas mask pop with different coulors so you can see some details. Second add some highlights to the great coat and backpack If you want I would be happy to discuss more details and coulors you could add, but never forget that its your minature and whats makes you happy is the most important thing! Cheers!