Hand wash it, but use normal hair conditioner instead of soap. When you lay it flat to dry, try to gently pull in back into it's regular shape.

Try mixing the vinegar with some liquid dish soap, a la:

Soak the hard water deposits in vinegar and they should dissolve or get soft enough to be scrubbed off. Soaking a rag in the vinegar and laying it on the offending areas works well. Re-vinegar the rags as necessary. This can take hours, but it works on hard water deposits better than anything else. Soap scum is a…