I wash my hair with clay! I usually use bentonite clay.
I too wash my hair first with a liquid cleansing agent for the sake of removing oils and whatever has built up on my scalp then I do a conditioning cleanse with Terressentials (which is mainly bentonite) and condition after.
I actually don't have to condition after using the clay/mud wash, but I do it anyway to baby and pamper my tresses.
Sometimes I make my own bentonite wash but I usually use terressentials because the consistency of the mix is much more even. When mixing bentonite with water, it really clumps and lumps which I don't like, especially when those lumps get caught in my hair. For me to get a smooth consistency, I have to use a vinegar which is great on the face, but I've never been too sure about using in my hair purely because ACV closes the hair's cuticles and I'm trying to remove toxins and a closed shaft will make that harder. I could just dilute the mixture with more water too, though. I've never actually attempted the acv/bentonite mix so I think I'll just try it when I'm running low on Terressentials.
Anyway, bentonite is freaking great on the hair. If you think you don't have any legit curls or definition to your hair, bentonite might change your mind. It is literally the only thing that makes my hair have defined and clumped curls.
Even when stretching my hair, my hair will have those little uniform waves you commonly see on looser kinky textures which I never get from anything else. Bentonite is gentle, REALLY softens up the hair, and ultimately does everything right, including detoxifying your scalp.
I'll try rhassoul clay someday.