How can I use Emacs tramp to ssh to a remote host and edit a file as another user on an ad-hoc basis?

/multi used to work for me, now it's gone and I'm frustrated.

What I want to do is, in my dream world:

/myuser@remotehost:sudo:anotheruser:/some/path/to/file

...and have ido-mode work.

The key thing here is that 'myuser', 'remotehost' and 'anotheruser' are all very ad-hoc, I use a huge array of remote hosts, often with different users and sudo-ing to a wide range of different users.

What do I need to add and how can I test it without reloading emacs over and over?