About sexual stuff in general: you can take the sensations building up sexual arousal and making them flow throught your body, directing them to more sensible areas of your body (hands and foot for me are very useful), expanding them and so on, until the thing becomes very plaesent and whole-bodied.
What I have found is something like this: if sexual sensations can flow, they are just very plaesent sensations moving throught your body; the moment they become painful is when they hit some kind of blockage, and then desire/irritation arise; if you find the point when plaesent sexual sensations hit a wall and turn into desire, you can use your attention/intention to make them flow there, and then desire is gone, and you are left with blissful sensations flowing.
So, to answer the question: the more you get used to enjoying sexual arousal, the less there is desire.
What can go wrong (meaning, what went wrong in my experience):
-if you put your attention on a single spot for a long time, it can get dangerous; if attention is more open, moving, then it's safe
-bad emotions can arise as a consequence of theese practices, as they can arise as a consequence of any other kind of meditation; however, there is something really particoularthat happens when they are combined with sexual excitement that makes them plaesent and painful at the same time in a very weird way, like you want them to stop but when you get away you want more...
-Painful sensations can arise in the body, in a way that is similar to how they can arise as a consequence of the Goenka tecnique
-since theese sensations are unlikely to go away at will, at the beginning you might find yourself nervous in daily life
On the other hand I noticed that, if I have semi-orgasmic sensations going on in daily life, they tend to make me more soft and open, in the same opposite way that if you have some chronic pain this will likely make you hard and irritable... as far as I can tell, apart for the fact that are obviously plaesent, this is one of the best thing that comes from sexual-oriented practices.
For more info on sexual stuff, see
Yogani's Tantra lessons...