Think of your hams as a forearm and your butt as a bicep; you won't be able to work the biceps if the forearm can't hold the weight. Now once your forearm is able to hold the weight you will increase the weight which can now start to work the bicep. Does that make sense? I always tell clients that if your form is in check and an odd muscle still gets the brunt of the weight then this is a muscle that needs to be brought up.
If you need to tone then you either need bigger
muscles or
lower bodyfat. I can't say how much size you have, all I can say is that you probably have a lot less than you think you have. Did you see this
video? This is what a female figure competitor and a female bodybuilder look like. To look like the bber you will need gear. To look like the other girl you can work your ass off and very rarely achieve anything better without gear. You might even be able to take small amounts (by female standards) and still not look like that.
http://vimeo.com/25071533
If you are gonna workout, then you might as well target the muscles you want to work. What is it that you want to improve with your lower body?