Are you planning on having your ducts cleaned? Have you had them recently cleaned? You need to know the proper process to avoid being ripped off. When discussing options with a cleaning company make sure they are licensed contractors and ask what standards and methods they use. The entire system must be cleaned using NADCA standards or you’re getting ripped off. Yes, use a brush to clean the dirt off, not airflow. Airflow is how the dirt got there in the first place, how is it going to clean the dirt off?
Any claims of mold should be checked by a competent inspector (not a remediation or cleaning company) who performs testing!!! I’ve seen dirt patterns that look exactly like mold and also the type of fungi sometimes tells more about what the water issues are. DO NOT USE “FREE INSPECTIONS”!!!!!! I can’t stress this enough, they are a business, not a charity.