i use references a lot!! sometimes i directly trace over a pose from posemaniacs or something similar, sometimes i use stock photos/figure drawing ref sites or pictures of myself, sometimes i look at other peoples art and get a sense of the overall gesture and try and come up with my own thing without directly copying them. and of course i come up with stuff off the top of my head. for erotic art you really just gotta reference actual porn if you want a solid understanding of anatomy. the initial sketch is by FAR the hardest part of art for me, so tracing can actually be a big help.