You can find out where airsta billet's for OS's are, on peoplesoft and CG Central. Just keep in mind that airsta's without C-130's have OS billets that will not be part of the flight crew.
The only pre-req I know of is to successfully complete a flight crew physical including a swim test and such....
As for what they do, I don't know but If I really wanted to know I would contact one of the OS's filling one of those billets and ask.