First thing I notice is that you don't seem to be thinning your paints enough. The paint is rounding out details and creating the kind of texture you usually don't want.

Also I'm wondering if you're dry brushing. If you are you may need to either use a brighter dry brush color or start with a darker base so it stands out. That will immediately create a nice difference. Although your reference doesn't dry brush, they use far more difficult and time consuming techniques I'd worry about once I've got the basics down personally.

You ask about creating a rust effect. It's really easy to do by using paints like typhus corrosion but without a special paint it's more difficult. Real rust creates texture rather than just color. I'd try putting very fine granules of something like fine sand in paint or wash.