Im not sure if you mean nsfw for artists or nsfw as in nudes. however ive seen lots of people just straight up use the tag nsfwtwt with nudes. i think its mainly about finding nsfw creators you like, following them, and posting stuff that appeals to the nsfw side of things, lots of the (smaller) creators you follow will notice you, might check your account, and might follow back! Also commenting on peoples posts, especially repeatedly helps. ive got several followers that dont even post art that i notice and follow because they so regularly interact with my content. I cant say much about making friendships that involve messaging and calling since i dont do that with any of the mutuals or friends i have on twitter, however i find connection in commenting on their stuff and interacting with them, and them interacting back. ive gotten closer with people by just following with people, following their private accounts, and being invited to discords because of it, adding my opinion on controversy they face, sticking up for people, etc