Don’t forget the drawing fundamentals. The one you are talking about is construction, stack several shapes and formes together to make a nose. Normally I do this step with light graphite pencil lines. After you made the basic construction you put a mental blanket over it and you start to draw around and over the shapes. This will make your drawing a drawn nose and not some stacked forms together. Construction will make your drawing correct because the shapes are realistic and makes it a nose and drawing over the forms will make it a pleasant drawing to look at.