Which app you are recommending for brute force? And is it possible to brute force second password on MultiBit/Blockchain.info with that app?
Thanks.
What you need is already mention above you can use the BTCrecovery tool to bruteforce the password of Multibit but I don't if it will work on Blockchain because their wallet is not the same as before but you can try.
Follow this tutorial on recovering your password for both multibit and blockchain from here
Complete tutorial on recovering a password.