Anyone have any advice as to how to help a very shy child?

Know, accept child. First you must get to know and understand the child, how they express and perceive love, affection, and how they acknowledge the presence of another person. You need to accept them right where they currently are in that process. Then supportive, behavior shaping and reinforcing interactions can be developed. Small steps to adjust their comfort zone are essential. Apply the "love language" idea.