I've used the mud too, that's why I asked. I've also used it in a soleseife, so not my usual HP. That thread should be in the gallery somewhere.
I used it just like any other additive, added it to my oils and stick blended it. I didn't allow for any water though, I just guesstimated and adjusted my lye ratio a very little bit. My mud is really thick.
I can't definitely say that using the mud in soap is beneficial to the skin, but I can say that it is lovely soap to use lol