Before I came to DTO, I had also purchased a full range pencil set. I’ve got pencils ranging from 8H to 9B.
From what I can tell, the reason for a full range of pencils (besides extra revenue for the manufacturer) is based on the system of constant pencil pressure. The idea is to use your natural pencil pressure at all times; that is, one single pressure – not pressing harder for more darks, nor lifting pressure for more lights. To create a gradient using this system, you would have to use a harder pencil for lighter values and a softer pencil for darker values. Layering your marks with a single pencil would also create a gradient for a very limited value range.
It’s an interesting idea in theory, but I personally prefer Matt’s system of using one pencil as it’s simple, effective and removes the extra variable of when to use which pencil from the learning process.
These days, I typically use two pencils: a harder pencil for the initial lay-in, and a soft pencil for modeling and rendering.
Two amazing artists that I know of who use a multi-pencil approach to great effect are Darrel Tank (he uses a 5 pencil system), and David Jamieson (he uses a pretty big range of pencils). Both of these artists create stunning drawings.
Matt uses one pencil to create stunning drawings. So the bottom line is really all about practicing the techniques of value matching, drawing accurate shapes, minding your edges and putting in the time to develop the skills to create masterful drawings.