Ah, no, don't use a hair dryer on a mirror to dry up the water!
Any water carries some solids with it and you want to work the water off of
the mirror while it is still water. Dragging a paper towel across the
mirror without pressure and making sure that the water follows the towel is
the better way.
There are several good articles on cleaning optical surfaces on the web so
go find them and read about what you should do.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!