So multiboxing and general mist alt usage is one of those arcane bits of Spiral Knights that's generally discussed in hushed voices, and only practiced by a few adventurous souls. Personally I think it's a really fun technique for mid to end-game players to mess around with and breathe new life into old content.
In order to demystify things a little, I put together a video of me multiboxing snarby:
http://www.youtube.com/watch?v=oKySEAw_V8c
I only used one alt in the video for the sake of keeping things moving and because I haven't actually created any others, but it'd certainly be easily doable with a full load of three alts. Roarmulus should be fairly easy to do with three alts all the way up through the boss fight, and RJP might get a little sketchy on the boss fight depending on what your gear is. Doing FSC with three dead alts would be quite the challenge, and I would be happy to see someone else attempt it.
I, shamefully admit that with this account and my steam account, have done IMF a few times multiboxing, because double the tokens really speeds up getting the rewards, and at the end of the day I only saved 100 energy, so in retrospect this isn't totally illegal IMO, it's just a touchy subject