I wash my locs with a mild shampoo and I spray my locs every day with a concoction that consist of Water, Glycerin, and Castor Oil. Your Friend can do a Deep Conditioning with Castor Oil and Olive Oil which will add much needed moisturization and conditioning to his/her dull and dry locs.  Your Friend can also refrain from washing His/her locs with shampoos that strip too much natural oils from the hair and scalp.  He or She can utilize a conditioner that isnt too heavy and is easily rinsed out. He or She should avoid products that are high in petroleum jelly/petrolatum, and also Beeswax & hard butters that are hard to wash out without using extremely hot water. These substances may cause build up inside locs that lead to locs with a dull and dried out appearance. He or She should Moisturize/Condition there locs on a daily basis because well moisturized locs are less prone to breakage than dry brittle locs.