I haven't noticed a sulfur smell but I almost always use this filter:
That said, most if not all of the places I camp have city water supplies. Years ago I rented a house with a shallow well. The sulfur odor was not so much noticeable after a shower but it sure screwed up iced tea. The research I did then said you couldn't filter it out. It looks like there may be solutions now. Out of curiosity I looked around and found this:
Most of those systems are large and expensive, probably not for trailer use. Here's another source:
Since you mentioned showers, is it mostly on the hot water? The second link mentions an anode rod in a water heater can cause the problem. MOst Atwood RV heaters don't have one - what do you have?