Aand Ill be the outlier - I coarsely ground some and added to my soap and I think they add a nice gentle scrubbiness. I didn't add them whole to avoid the mouse poop thang. I did this for both HP and CP, and honestly I like the CP better, but maybe that's just me - Ill scare up some photos. Oh and I soak them in my lavender EO before mixing them into the very thin trace batter (CP) or at the cooldown (HP), and I think it makes the scent stick better. But you WILL get drag marks when you cut, unless you use individual moulds.
Another thing you can do is dry them super well and grind them super fine and sift them after you pour half the soap to make a pencil line, that's worked very well for me.