Hey Glenn... Is it possible to saw me a close up of the German helmet in the display case? Not the one on the stand but the other one... From that pic it looks like it has a paint like the one i found in Crete last summer!
Maybe wrap the head in foil or cling film / saran wrap, then wrap it in cloth like an old OG T shirt for aesthetics.
Apparently the best thing is unbleached cotton muslin. You can get it cheaply from any fabric store, and it's inert. I've read to wash it without any soap first, and then it's good to go to wrap styrofoam heads, store flags, etc. I've bought some but haven't used it yet.