yeah, spot reduction is a myth. simply put, there is no such thing. I'm not too sure if exercises are the way to go to reduce the ass, seeing as it is a muscle and all, and exercises tend to increase the size of muscle. although in theory you could possibly do ALOT for it and overtrain it to the point that you loose muscle mass, but I would suggest not even trying that seein how closely related you hams and glutes are. Cardio seems to be the only option, unfortunately, in the grand scheme of things, the fat around your midsection and ass and thighs will likely be the last to go, so it could take alot of cardio. I would suggest, as much as i hate this, the stationary bike. working the muscles in your legs and but might increase your chances of loosing the weight in the places you want.
good luck