Figured i’d post about it here , because lotsa people were really excited about keyshots addition of polypaint support goz plugin , but that was taking ages and finally got scrapped to be put into the core of keyshot, but no one knows when or how now.
Personally i prefered marmoset over keyshot and i didn’t even know they were planning on adding this, but apparently they did.
So you just have to save your OBJ with polypaint on it , then in the material in marmoset put the shader on vertex color and enable sRGB and your polypaint shows up.