Nice screen shots!
I downloaded "Zombies of Nightmare", too.
the_rex, The Helios,
I attach Ageha's ".psk" files here.
This model used 3 UVmaps. "Face" and "Body" of the main part made from "LittleEris". "Booster" which was gathered from "KouRyuu".
Among this, "Body" and "Booster" were arranged perpendicularly and joined to 1 UVmap. So, "BodySkin"'s size became 1024x2048.
Therefore, if you take the UVmap by UPaint, it is shrinked perpendicularly. So, please double it perpendicularly when you use it for Photoshop.
UPaint is convenient to make a rough-sketch. However, UPaint displays a model like the all polygons were connected smoothly. Since it can not see where are sharp corners, I attach the screen shot in LightWave for reference.
At "FaceSkin", since the alpha channel is used for the hairstyle, it can not finish by UPaint.
I hope some good works will be made.