Anatomy is always something to improve when it comes to sexual art. Not need to know how to draw it milimetrically, but practising a "per***al anatomy dummy" with notions of real anatomy, it makes the whole thing lot easier and it makes you go faster to the second part: details. Detailing the dirty parts (textures, lighting, liquid consistencies) it helps to make it more naughty, so that means more happy clients willing to pay for their fantasies to be drawn.