I have pages in various social networks, I talk about my project, I use my design in advertising.

But the problem is that promoting content for adults is always very difficult.

Please share your ideas where you can create an advertising campaign on which sites with adult themes? 

Can someone share his experience as he promoted such a project?

you should  make a video  with a small part of example and upload it to every possible adult viewing platform.  This kind of trick as been used for websites on membership.