In concept, fogging your ductwork after removing the debris with regular air duct cleaning is a great idea. However, it is important to understand what you are trying to achieve and not be misled with expectations for amazing results.
The bottom line is, disinfecting requires scrubbing, allowing for dwell time, even surface coating, and multiple applications of a disinfectant. Simply fogging your ducts is not disinfecting. You also need to make sure all surfaces were coated, allowing the appropriate dwell time, wipe them and reapply. You can’t wipe parts of your ductwork that are deep inside your system. Also, applying disinfectant and wiping can damage metal ductwork, causing it to rust at a rapid rate. If you are hoping to remove mold, musty smells, and smoke contamination from a fire, you need to replace ductwork rather than fogging. You will be dissatisfied with the long-term results of fogging.