I have some powdered soapnuts (reetha) that i've never used, i might try them though.
My reliable one is Shikakai, though i don't have just one way that i use it. The simplest one though is i add a few teaspoons to a jug and pour on some boiling water, stir, leave to cool down then pour over my hair working it into my scalp. I leave that on for a few minutes then rinse and apply whatever conditioning concoction i'm using that wash.