Having aircon on will always help clear moisture from screen, turning temperature up will make it even better. The hotter the air is the more water it can hold, and as ColinS says, the flipside is that the cooler air gets the less moisture it can contain which is why a cold night after a warm day deposits excess moisture as dew on you car and lawn ( or frost, depending on how cold the night is). The combination of aircon and heater works because aircon cools the air which makes it dump moisture and then heating this cold dry air up makes it super dry and eager to absorb moisture.
When you have a dedicated screen clearing button in your car as mk2 onwards have, it turns on the aircon on and fan to full speed to clear screen as quickly as possible.