This is awesome. Modeling aircrafts I have used similar technique to apply wash to bring out panel lines, similar to what you are showing with filter, but the excess is wiped clean and it’s always, well most of the time, applied on gloss coat that protects the main paint job. So, it’s easier to whip off. From what you are showing in your filter prep sequence pics that cup, looks like 3oz clear cup, is half full of thinner with only dap on paint. So, basically it’s like a colored thinner?
Btw, applying your filter on flat coat paint…would n’t that make it hard to clean up and hard marks/stains on the paint even after cleaned? I figured that out by making a mistake of doing such on a bottom of an A-10 wing where I forgot to seal the main color and the wash left hard stains. In the end I just had to repaint that area and start over.
Anyway, great bit of information. Keep of the good work.
Mike