How to Coach Anyone: From an Expert to a Novice
It's a valid concern, as static time management systems that present fixed habit patterns often miss the mark with clients who fall at the low end, or high end of the skill spectrum. As their Time Management 2.0 consultant, you need not worry, however.
First, if you are consulting with them it's because they experience a current gap, or expect to face one in the short term. That gap is the cause of symptoms they hope to mitigate.
Second, at the end of your work with them, they actually need the same things: a handful of behavior changes that they can safely and successfully implement because they have the right supports in place. The exact number of changes, and the choice of supports must be discovered by working with them.
Third, when working with someone with low skills, the key is not to overwhelm them with too much. Make success easy by focusing on small steps.
Fourth, when working with someone with high skills, don't box them into anything. If your diagnosis shows them to have super-human skill in time management, don't panic. Just use the principles that you know and understand that you must look for the Kryptonite... their areas of weakness. Then, don't pretend to have the answers. Instead, bring the right questions and discover what small changes they need to focus on making in the short and mid-term.
Just to reinforce the point... remember, you are the expert now because of what you know, but because of what you know what questions to ask which leave both clients at the very same place: with a plan for improvement that looks doable to each of them.