The DG is basically state-of-the-art when it comes to web tapered design. That said it will probably take a computer program or at least a fairly complicated spreadsheet to properly utilize it. An MBMA task group has begun working with Dr. White on an update / addendum to the guide to address areas that were not completely covered the first time, such things as tapered sections with a change in taper within the braced length, axial loads applied at some location other than the ends, etc.
The primary approach is that the overall section is analyzed somewhat globally, i.e., analyzing each cross-section along the braced length strictly for the forces that are determined at that specific location is not sufficient to fully establish the performance of the section.