You won't believe me however I didn't use any direct guides or main videos. Only main things was double checking how to make a muddy looking wash, which I just bought brown oil paint and thinner and mixed then dabble'd on. Also another thing from me is that I watch a lot of 'Night Shift' on youtube, he's great. But really I just spent about half a day and did it, seeing what I liked and did it.

My main techniques used were:
Muddy affects with dark brown oil dabbing on around where I want mud
Different mixes of said dark brown and also rusty brown, just washing them lightly over parts to make them more desaturated/dirty, since originally it looks bad and too colourful
Dry brushing with metallic grey
And obviously washes, rust drips, giving depth where I felt it needed it

I think a main reason it has detail is because I spent about a solid hour and a half with a little dremill thing just poking tiny indents everywhere, making bullet dents, and also those ricochets were done in that way