To confess though, I was a bit out of my depth initially regarding the worn-faded paintwork (not so much the fading).
Obviously the paint layers come through from below on the prototype and trying to make it look that way rather than other way around as it is on the model - for me - was tough.
I tried 2/3 methods, more by accident than design.
Essentially I put the chipped-damage layers onto the Masterpiece gloss top coat first, then worked over those (once dry) with the various semi-transparent oil layers. I then gently satin varnished over that and once dry, added some more body colour marks of slightly differing shades over the satin varnish (AK Acrylic) to gain the effect(s).
Hope that’s useful.
Neil.
Yes I would agree that, having weathered my own models, creating the faded look is tricky without making it appear as if has been 'added'. In some ways our modelling approach to weathering is akin to painting in oils starting with darker and working towards lighter colours. And of course there are the areas where muck, mud and grime stick around leaking oil and the brake dust 'burning' itself on. Let alone the cleaner areas from constant handling and/or walked upon.
Naturally in the real world paintwork is attacked by exposure to the sun (bleaching and UV light), attrition by minute abrasive particles carried by the wind and washing/scrubbing by rain which can be acidic or alkali depending on what it has absorbed during it's journey.
As I paint my own models I'm now working on trying to treat them like watercolours by starting with a thin coat of the base colour and add additional washes and/or coats to the darker areas where I need them, leaving the areas I want 'faded' untouched. This is still
work experiment in progress. Then when I'm happy I'll add the muck and grime where it's required.