In your level II material you learn that the skin is part of the lung system, and the colour associated with work on this system is white.
As Michael says asking your master's energy to join with yours to heal any particular conditions is a very good practice. The more specific the request the better. Once you make the request of your master, who is a person you are confident will send their energy to help you, you believe that the healing has started. You do not judge the process, you probably don't know what is involved in the healing. Have faith that it is progressing in the right fashion for you.
I've started to introduce my daughter to SFQ and I remembered Master Lin's words, "Where the mind goes the qi will follow". This is something I have strongly experienced. In this case I would interpret that statement to say that when you ask for healing of your conditions, visualize the healed skin as completely and strongly as you can, in the completely recovered state.
You are perfection.
Iam2 