Convert Sims 4 skin as body overlay mask in Sims 3
I'm curious if anyone would be able to help or point me to a tutorial for this. I've searched a bit but had no luck myself--probably because what I want to do is so specific and obscure.
Basically, I want to take
this Sims 4 skin and turn it into an overlay/makeup mask for the Sims 3, so I can combine it with a custom skin. I think it's doable using CTU, but I'm not quite knowledgeable enough about Sims modding yet to know how to go about it. Specifically, I know I can edit the texture in GIMP (done it plenty for the Fallout games, and even released a new outfit texture once). I just don't know how to then get that texture into the game as a costume makeup that covers the whole body (or as another CAS category that can do the same--maybe an accessory). Can anyone help?