>>9810992I think what you want is detailing and weathering. What bothers you is how the panel gaps or lines in between different mech "parts" on the same plastic piece are the same color as the rest of the mech, and that it looks too clean, right? And that's because it makes it look like a plastic toy instead of a (war) machine. The panel lines have a simple fix. Just use some black panel liner and get some enamel thinner to clean up the excess. But you can go for a realistic paint job if that's what you meant too.
https://m.youtube.com/watch?v=7-5IRey5wtI 