I've never done this myself, but I heard that if you soak fresh herbs for several weeks in olive oil, the oil will become scented. I go with eo myself, it's quicker. I've used rosemary and sage dried herbs. To make the powder real fine, use something like a coffee grinder. I put the herbs in a few minutes before pouring the soap. They could have been left in longer for stronger coloring. The herbs do make the soap kinda gritty. I like that, but some people may not. The herbs did lightly scent the soap, but I added some eo to increase the fragrance. Also, the soap could be filtered if you wanted a smoother textured soap.