Make A Natural Herbal Shampoo Add herbs to boiling water, allow to seep 8 hours. Strain out herbs and compost them. Add Castile soap to the herbal infusion. Add 20/30 drops geranium essential oil. Add olive oil depending on dryness of hair, for more dry hair add a tsp, but less dry add 1/2 tsp. Shake well to combine! At shower time work from scalp to ends, shake well before each use!