"Very good tutorial. When doing brick sills under windows with diferent sill heights on the same wall. do you one create segments of a sweep, or multiple sweeps?"
Here is a quick tutorial to answer that question. You do not want to model a brick sill within the project. It is much easier to model it within the window family, lock its parameters, and it will update to the many different window sizes. This is a pretty basic tutorial (I think this is a tutorial for the Revit 5.1 tutorial book).
P.S. - I recorded the video very fast. If you are really planning on using this I would definitely suggest placing the brick sill inside the opening void and creating the correct sill detail.