Best solution is to just use the Aircon. turn it on full temp and full fan. It will clear the windows fast.
The demister function on most cars does not use the aircon. It is simply a fan boost with an electric heating element that changes over to the heat exchanger as the temperature rises, this takes a fair time to generate the heat required to demist, but is less draining than the Aircon is on a cold engine.
Your Aircon works fast because the dehydrating ability of it will dry out the air and clear the windows much more quickly even when cold.