Use a baking soda wash or a non-residue shampoo like Prell Classic (don't use it too much, it can be drying and cause dandruff because it's a clarifying shampoo and is meant to be used every now and then). You can try baby shampoo also. The baking soda wash is the most effective but you gotta make sure to make the recipe properly and dissolve it in very hot water, and rinse with hot water also. There's lots of recipes on the forums if you search.
I'd steer clear of Lavendar, Tea Tree, and Peppermind oil's though because they can cause gynecomastia in some cases and proven to decrease testosterone/increase estrogen. There's stuff on google about it. Peppermint oil can even slow hair growth, some people tested it on one side of their face for their beard and noticed that. Weird huh! Lol.