Keeping as much humidity out of the air as possible is key. What we do is keep both roof vents open (have covers over the FF's) until bed time. If we cook or shower at least one of the vent fans is running until cooking (& clean-up) are over and shower is wiped down...you will cut down on the moisture in hte air if you wipe down your shower and then dry the towel(s) -- don't air dry them (unless vents are open & fans are running) them or you will continue to add moisture to the air.
We don't like to keep the vents open all night or the curtain open and the above helps a lot.
2011 Airstream Classic Limited
2011 GMC Sierra 2500HD Duramax/Allison