I'm not into FS for my paid erotic encounters. I much prefer a hand job or perhaps a blow job. I'm immensely visually stimulated by seeing her hand or mouth on me, so that really does it for me. With a hand job the woman can be close to me (faces close) and we can view the action together. This is highly erotically charged for me. We're all individuals, so of course others are unique in what turns their crank, but that's what gets me going. Side benefit is that those extras are almost always less expensive...