Trader Joe's sells little yellow microfiber cloths that really soak it up in our FWC Finch and are easy to wring out. Don't remember what they cost but think they're super cheap.
Trying to find the balance when it's cold out between enough ventilation to keep it from raining (or icicles forming) inside the camper and not either freezing our butts off in bed or getting blasted out by the furnace always seems to be a struggle. Running the vent fan while cooking, especially when boiling water, definitely helps. If it's not blowing, raining or snowing too hard out, so does opening up the windows some, putting on a warm hat and long undies, and laying an opened up down bag over our zipped-together, classic, flannel-lined Coleman bags.
Thanks for the Hypervent recommendations. I'll try to track some down.