I use an oil heater unit (radiator style) that I plug in in winter. I keep i at a temp thats almost comfortable (55-60F) which should always be above dew point. I checked this morning and all windows and surfaces are free from moisture.
From what I read and others here advised a couple years back, electric dehumidifiers will dry the air but since the camper isnt sealed, i will be drawing in humidity from outside. Heating the air doesn't remove moisture but it does keep condensatiin from happening (for the most part).