You can only really do it programmatically. All the backup/restore in MultiBit HD itself are based on you knowing your wallet words.

If you have a look at :

org.multibit.hd.core.crypto.EncryptedFileReaderWriter
org.multibit.hd.core.crypto.EncryptedFileReaderWriterTest

that's the code that encrypts and decrypts the wallet files with the password.

The codebase is here:
https://github.com/bitcoin-solutions/multibit-hd