Where are the pornstars listing or is it a case by case thing?

Best place to start are the main agencies that specialize in PS providers. Trystagency, PC, AIA. There are also a number of assistants who have their own lists, you can probably find some of them by doing a search of this foru,

Lke most of the real good stuff here you need to be a VIP member.  Then the Provider Search form will let you select all sorts of characteristics.  There's a Porn Star cehcbox

For advertisements go to the buzz boards. TER changed the category name a year or two ago presumably so it's not as overt advertising.

Porn star buzz board is kinda dead. Not much activity. Trystagency, PC, AIA, and Lourdes are what I’ve found as best bets for info.