Hmm. I'm not sure if I completely follow, can you post a picture?
There are a couple of different options for adding points to a shape after you've created it. Slice surface is handy, as is the knife tool. Probably the best tool is a plugin called "divide loop" that you can download here if you don't have it already:
http://supercoldmilk.com/ac3dplug/divloop.html
I made this short video showing some of the tools, maybe this might help:
http://www.independentdeveloper.com/files/curves.wmv
Oh, also the spline tool is also handy for creating smooth lines.