Mate, I really like how this is going. Some fantastic work/research and effort going into this…
Just a point from me … sent in good faith and as feedback …
Ref the image above, The 2 red circled areas look superb, and to my eye, they represent the ideal and totally realistic way rust develops and scabs off etc.
The rust patches in yellow one looks a bit to uniform (on both sides) like Tim alluded to and could do with a bit more randomness ? (not even sure thats a word lol).
And the grey overall looks just right. I walked past one like that a few days … Great work mate.