Most of the girls use Facebook, only a few of them I know use twitter.
Best way to find out is to check out the babestation/partyland twitter page and check who they're following, you should find the girls who work on the show.
Seems to be an even split between girls that have an "add all" policy and those that don't - which is fair enough, these are after all fantasy services - I found Charlie C under her real name on Facebook and she didn't accept my request but I respect the fact she probably just wants to use it for "real life" family/friends stuff and remain a massive fan lol
I saw one guy on Ruby's facebook a few weeks back moaning that he'd tried to add SJ a number of times and had been declined - seems a simple "do the maths" one to me - some girls are happy to add hundreds of fans, some obviously don't wanna take their work home.