I don't use anything but hot water and "vigorous agitation", no. Though as noted I do end up using shampoo (diluted Dr Bronners) on occasion. For the rest i use a coarse washcloth, and I think I come out cleaner than those slathering themselves with "product". I'm currently talking myself out of using soap on the pits, though I think it will take much more time (and probably some other lifestyle changes) to stop using it on the nethers.

Not op but I use some coconut oil, lime juice, and cinnamon concoction my wife gives me. Maybe every 2 or 3 weeks. It’s great and I have zero complaints about my hair or scalp. I’m pretty sure it’s from some recipes online or amalgam of recipes. I don’t use anything else except water when showering in between.