For the first time I made my slave lick clean my dirty feet. I walked barefoot for almost two days so that he could have a proper challenge and then I order him to clean them. He struggled a lot expecially at the beginning when he gagged a few times while swallowing the dirt, hairs and crumbs from my feet. I checked a my soles during his cleaning till they were pretty clean and I can say that in the end he did an accettable job.