probably no rust, I don't know about mud yet. I'm still trying to make up my mind about that.
He probably will get a dusty/dirty look. There probably will be some spatter involved but not a lot. I would personally choose a darker color for the mud so it doesn't stand out too much Against the tank colors.
After the character I'm doing now I'll probably do Longarm so I still have some time do think about it though.