Here is my submission to the bounty https://steemit.com/steem/@jga/msteem-multisignature-transaction-app
I used the account @fulanitodetal.
This is not just a guide but also a webpage to modify the authorities, and sign any type of transactions using multisignatures. It works on the browser, no need to install software.
Awesome, thanks! Unfortunately you did not qualify for the bounty because there were already four submissions ahead of yours, and the bounty was awarded to the first person to submit a valid entry. I did send you 50.0 STEEM from an anonymous donor though as a "thank you" for your contribution :)
Super! Thank you very much!