Find some nsfw art forums and things like that, post previews or art or something, leave links to your work here. I don't know much about the nsfw market but I would imagine, just like with everything else, you need to go to where people who want that content hang out, and put it in front of them, in order to drive traffic to your work here. Find subreddits, forums, and other boards, art sites etc. that have congregations of people who are into the same kind of content you are making, and don't spam the boards, see what is allowed to post there, whether it be previews, art, or just a text introduction post where you talk about your project and make sure to complete your profile with links to your work here, etc.
Hope this helps you brainstorm.