I wrote about my first experience with it here:
thereThe method works on the assumption that with less tension you can feel everything in more detail and thus you are more able to feel new ways of doing something. So, the 'lectures' in this method are assembled in a way that leads you to discover the 'optimal' way to do it on your own. In every lecture you'll take the whole body into account, but there are some with focus on the back. You do small movements in a certain way to discover how the body parts work together and usually discover that those movements can be done easier than you're doing than now.
So, I would suggest finding a lecture that teaches control over the back. But that's not necessarily the best way to proceed - if the pain is in the lower back, that doesn't necessarily mean that an 'error' in the lower back usage is actually the reason for this pain, it might as well be somewhere else.
There are also trained Feldenkrais practitioners who could look on your problem in detail and probably find out a solution for this. Sadly, they're rather expensive.
So if I was in your situation I would just walk into the next library and lend some books such as this
Awareness through movementhttp://www.amazon.com/Awareness-Through-Movement-Easy---Do/dp/0062503227/ref=sr_1_1?ie=UTF8&qid=1368085127&sr=8-1&keywords=awareness+through+movement
which contain instructions for some lectures. It's not easy to get the feeling for how it's done best, so one lesson under a teacher (first lesson is usually free) might be a good idea.