Probably one of the harder effects to get down if I'm being honest, partially due to limited resources.



For what is out there, however, then using transparent images of mold, vines, mold, etc can create this sort of effect. Most of these actually don't use an altered layer effect, rather I adjust the lighting on them to make it fit with the character, as well as adding a texture to the character to make it look natural.



Using tools that contort the shape of an object also helps smooth out the mold/vines so it looks like it's contorting to the characters limbs naturally. On Foxy's hook arm, you can see that they curve along the path of his bent elbow.