So the link you have there for site designer is the addin by autodesk i mentioned. I haven't used it personally yet, I hear it is ok for basic stuff, but it isn't what people were hoping it would be.
So this link is to MARCELLO SGAMBELLURI AU class. Well worth the watch. It has 3 techniques depending on your needs all based around similar principles of DWG Importing.
http://au.autodesk.com/au-online/classes-on-demand/class-catalog/2013/revit-for-architects/ab3340#ch...
Next is a technique using spliting & merging of toposurface. The instructions I felt weren't very clear, took me a few goes to understand what they were getting at, but it does work fairly well. My advice for this technique (as mentioned in the blog) is to completely sketch up the outline of everything first using lines. Makes it much easier to edit after if required. Since you can't snap to topo edges, these lines help a great deal.
http://bimtionary.blogspot.com.au/2010/02/curb-and-gutter-along-topo.html
My personal preference is Marchello's technique of creating a massing rig. It seems cumbersome, but when you break it down, it doesn't really take long at all. The toposurface merging technique is clever I thought, but I feel it requires more work.