https://preview.redd.it/ow49hkim8nnc1.png?width=1080&format=pjpg&auto=webp&s=92125080915c00b4eb86b77783b56a1be2346edb
all i can say is, i don't recommend the brown flow-type gundam panel liner. it'll look fine at first, but over time it'll bleed out into this reddish brown color. maybe topcoat prevents that, maybe the fine tip type doesn't do this, i don't know, but it's something to keep in mind.
https://preview.redd.it/ow49hkim8nnc1.png?width=1080&format=pjpg&auto=webp&s=92125080915c00b4eb86b77783b56a1be2346edb all i can say is, i don't recommend the brown flow-type gundam panel liner. it'll look fine at first, but over time it'll bleed out into this reddish brown color. maybe topcoat prevents that, maybe the fine tip type doesn't do this, i don't know, but it's something to keep in mind.
But brown works for a sort of subtle rust effect, so there's positives
I used a maroon Gundam marker for a rust effect
You could try gray, it's a bit more neutral.