If you have a GPU, you should try Hashcat (Free & Open Source) or Passware lab kit (Paid, Closed Source).

If you have a CPU, You can also take a look at the oldie one, BTCRecover, or, johnny (John The Ripper) but, these are way slower, and useful only if you got a real clue about the password. If you want to try all the possible combinations, don't use them.

I had an idea for a really long time about creating a software that will split the work between different parties, trying to brute force the password.
I just wanna say that it is possible to implement some kind of a brute forcer, that will brute force the ckey/mkey, (these are the encrypted private keys, not the encrypted password) much faster than what Hashcat does for example.
By the way, Hashcat will ask you for a hash. Get that using a script named "bitcoin2john.py"