Fundamentals look alright. One little thing I can chime in on though is it looks like you're not thinning your weathering paint enough, and/or not working to 'clean' it up enough after application.
With oil/acrylic weathering like that you want it to look fairly soft and diffuse, but the brush strokes are pretty distinct and obvious there on yours. Generally you want to get the paint pretty wet into a wash, then cover it all over where you want weathered. Then pretty much try to clean it off again with a dry rag. Idea being that you'll never really be able to get it perfectly clean again, with the grim staying in all the recesses and texture of the surface like real dirt and grime will. Depending on how thin/thick the weathering paint is, and how much you actually do try to scrub it back off, you can get various levels of weathering. From almost spotless with only grime in the recesses that thinner paint and more scrubbing will offer (good for smooth chrome surfaces that would clean easily irl), or a more general weathered film over the whole thing that thicker paint and weaker cleaning will give (good for more rougher materials or just things you want to look generally really old and worn). Doing it both ways with several different shades of paint can give best results for a diversity of grime.
A few brushed or splattered on bits can work well too for scuffs and grime splatter, but best to keep those pretty conservative.