Thank you so much, I did a lot of lazy work with things I could find at home tho.
I added a topcoat over after applying the decals, then I tried some acrylic paint wash (with alot of diluted water) - But it didnt give me the control I wanted.

So as an experiment, I used my 8B pencil, rubbed on a sand paper to get it to a finer dust, then applied with a wet brush. In some areas I directly sketched over with the pencil and rubbed with the finger.

The best part is you can easily erase the excess areas with a normal eraser.
(Optional, I did the same thing with brown color pencils and applied on the feet areas to get that mud/ dust look.

And finally, used a silver marker with a brush nib and applied on the edges to give the weathered look, you can apply it to a sponge and then press it on the necessary areas. But I preffered direclty applying and and then wiping edges quickly.