Before fading, I applied two filters on the model. Colors are chosen compared with the base color. Filters was often confused with washes. It's definitely not the same technique and the expecting result is totally different.
Filters is a highly more diluted enamel or oil mix than washes. And they are applied on the whole areas.
You must wait about 4 hours (for enamel filter) between to filters.
You process the fading until the effect seems good.
Before washes, I airbrush a thin layer of satin varnish. That way, I am sure the washe (diluted with enamel thinner) will not spoil the fading work.
For now, I use a dark wash of oil paints (asphalte + burnt sienna). I say " for now" because some other washes may be applied at the "dust stage". The wash is applied on specifics location like in this case around the bolt and inside lines if structure.
A long long (well very long I guess) paint chipping await and will appear in the next update.
Have a good (holy)day!