Using a hair drier??. Keep the vent open and run the fan. have another vent or window open. If your bathroom mirror is fogging up, then you are not getting the moisture out.
Its a pita, but part of cold weather camping. I open up the front vent to allow air in when I use the bathroom vent fan for showering. It allows the front of the coach to get cold.
I open the bathroom vent to allow air in and run the fantastic fan in the front when I use the stove. then the bathroom gets cold.
I run a small fan constantly every night to circulate the air. Parking at an open site helps also. When the sun comes up, the rig gets plenty warm enough to open the windows to air out or even run the AC for a bit. It gets pretty routine after a while.