I agree with the other two posts. In addition, you might turn on Modeling Relations under preference once you get your curves pretty
close. This way when you use edit/add point to add additional points to yoru curve, you can see the effect on the surface immediately.
In case you haven't used Modeling Relations, here is a little explination. When you create a surface with this turned on, the surface will
update when ever a change is made to the curves it was derived from. You must turn this on before you create the suface. Once you like your suface,
you can drop the relationship by using Effect/Freeze, copying the suface, or deleting one/all of the curves it is assoicated to.
Hope this helps,
Urp