Particular Case of RAR Password Cracking

[chants]

1) Get a better dictionary - find a list of all conjugated forms of the language words you are dealing with somewhere out there.
2) Generate your own dictionary - find a list of base forms of the language, find an exhaustive list of possible suffixes, write a small program to combine all combinations.

Really I don't think there are any tricks when you have such a specific situation beyond that you have already kind of guided this response.