Refrigerator Ice Maker Frozen Fan
The main danger is hair dryers is that you damage the freezer parts. If you elect to use one, use it on low or no heat. Remember, most modern freezers use plastic for everything they can, and hair dryers are designed to dry hair fast, not defrost freezers.

Compressed air will probably not do it. Compressed air will expand when you use it, which makes it cool down.

My experience is that freezers will freeze up with either insufficient drainage or insufficient air flow. Used to have a Kenmore that would defrost into a pan, but there was nothing to keep the drain in the pan defrosted. After a few service calls, a repairman installed what looked like a specific device to transfer the defrost heat from the coils down into the pan and that problem stopped. Another time there was insufficient air flow into the refrigerator from the freezer, and the freezer became too cold as a result.