I remember reading that there is a manual work around for the problem when the figure's materials are not correct for the automatic "copy materials" scripts that come with these genital add ons. Please note that i haven't looked for the original thread and this is from memory so might be completely wrong
It's a bit of a journey into the mechanics of how the 3d rendering process works, so you'll need a certain level of technical interest
The scripts generally look for the texture file used for the chest of the model and copies that to the image slot of the texture of the genital. Then the UV mapping of the genital is setup so that some part of the centre of that image is used. In some cases, the UV mapping (and thus location of the skin textures) in the model's own chest part are just not right for the uv mapping of the genital.
In this case, it's up to the user to work out how to find a better skin texture image, or copy and edit one of the skin images from the model so the pixels ARE in the right place for the genital texture. And then replace the genital's texture image with the better one.
You can use the Daz "UV Map" view mode to see the mapping of the genitals 3d model to the texture image( although this can sometime work pretty poorly). Alternatively, you might look at the texture packs associated with the genital to see if you can find examples of how the image should be located. If you are really hardcore, you can try importing the assets into Blender and look at the UV mappings there.