I wouldn't look to "systems" or "seminars" or "playbooks" or "coaching" or "game changers" or any other such nonsense. None of it will work, except for the hustlers selling you the nonsense.
If you want to know what marketing methods are used by Duffy, or anyone else who is successful, pull up a slew of their listings and follow along. If you see something good, copy it to start out, then figure out how to improve it. If you see something bad, delete it from your program. At some point, you will have to come up with your own original creative ideas to supplement what you have copied/modified.
And while you are doing all of this, make sure you are in close contact with all present clients, making sure they are taken care of to perfection.
If you combine rigid attention to current clients with creative marketing that is not duplicated by others around you, you will never need to worry about buying garbage from the legions of two-bit hustlers who prey on real estate agents who often seem to have a penchant for dreaming instead of doing.