indigo naturalis

I was wondering if anyone on curezone would have any idea about how to make a cream containing indigo naturalis for psoriasis. I ordered some from champori company but was disappointed because the cream was in a base of petroleum jelly. It was very greasy to use and I am concerned about the safety of using a petroleum product. I found a recipe for the cream which is indigo naturalis, petroleum jelly, yellow wax and olive oil. I am just not comfortable using the petroleum jelly. Any recommendations?????