Thanks for the heads up.
I was under the impression hashcat brain was necessary to check if a hash had been already cracked. In our case, we work on a very limited number of hashes (actually, 1 ). This is why I didn't see hashcat brain as a necessary. If it can help, I will still implement it on my server asap.

What do you mean with "sharing cracking resources with someone you don't trust" ?
I might be a bit naive but what can really happen ? Other than not being paid if the password is found.
Actually, it would be a really bad move.
I am sure many peoples are in this situation (owning a wallet file without its password) and if we can build a system allowing to better/faster find those passwords it would/could be really profitable for everybody.
Just my opinion.

Well, actually, only the wallet hash is shared. Correct me if I'm wrong but it can't be exploited to recreate a wallet.dat file.
Actually, I didn't configure hashcat brain. For a bruteforce attack, it is not necessary.
I don't believe brute force attacks are the way to process but let see how it goes.
Meanwhile, I'll try to configure a dictionary attack with brain and prince to check if it goes better.

I was following this topic for a while and decided now to jump in.
I don't know if I am allowed to post link here so I will provide it through private messaging.

I am sitting here on an old wallet.dat with 50 BTC.
After reading all the comments in this thread I decided to set up a solution to share wallet hashes (not the wallet file).
This solution also splits the brute force tasks among a hashcat connected network of computers.

The only knowledge required is to be able to install python (as well as 2 extensions) to run the client.
It downloads by itself the necessary files (hashcat, the hash files and, if necessary the dictionary files) and share online the resources with the others.

For me the wallet is lost, so if peoples are interest to jump in, they only need to contact me and I'll configure them an account to share the resources.

If we are able to find the password, I will share the 50BTC to all involved participants.