I also have Postherpetic Neuralgia and have had shingles in my scalp. Valacyclovir helps the episodes and I also take a smaller dose daily to ward off future episodes since I've had quite a few.

For the Postherpetic Neuralgia, I am now on 90mg of duloxetine and use lidocaine patches as necessary. They do make an ointment that might be easier for the scalp area. Physical Therapy has helped tremendously as well, I've learned what to do to get the nerve pain to subside in most cases -- it doesn't always work.