So, here is the model painted.
Once I had the basic upper color on, I added a little XF-51 Khaki Drab, and thinned. I went back over the various panels. I wanted just enough difference in color to emphasize the panel lines in the original color. Then I went over it three times, each time adding more XF-51 to the XF-74, and thinning it as a wash. I blotched it over the airframe, concentrating the lighter colors on the upper-facing surfaces. After the third, I added in some Violet, thinned again and went over it, then more Violet and concentrated on the upper surfaces. This is to emphasize UV-sun fading, since these airplanes did their fading in the ETO primarily at altitude, with strong UV light. I then added in a bit of XF-78 "Wood Tan" and went over the fabric control surfaces, since they faded differently than the metal surfaces.
When all that was done, I cleaned the brush and painted the Medium Green blotches with XF-5 Flat Green, a good match for US Medium Green. I used a jpeg of the boxart of the Hasegawa limited release of "Knockout Dropper" to see the blotch patterns.
I unmasked the leading edges where the de-icer boots had been but had been removed - there aren't a lot of photos of the entire airplane, so it is unclear if the de-icer boots had been removed before or after Mission #50. I went with removal because it looks better. These areas had been painted with Tamiya XF-16 Flat Aluminum before masking. Once the masks were removed, I went over the area with brush-painted Vallejo Aluminum.
Once the paint has had time to cure, I will apply an overall coat of clear gloss to protect the very thin paint, then proceed to decals.
The whole secret to sun-fading is to apply the additional applications of lighter color so that the original color still predominates. Once I have done "panel lightening" with the first additional coats, the thinner and lighter coats are applied by blotching, so they do not conform to any geometric shape in the surface detail, since that isn't the way airplanes fade.
Also, ETO high altitude UV fading will be different from that in the Med, North Africa, South Pacific, etc., When you're fading paint, you need to take into consideration where it was happening.
2 attached images. Click to enlarge.