I too have the Hot Rod add on. Each Fall when I winterize I drain the hot water tank by removing the Hot Rod. At this time I take a few extra minutes to clean the calcium & hard water build up from the Hot Rod heating element.
When I added the Hot Rod I mounted a small 30 Amp breaker box adjacent to the existing motorhome breaker box. This add on breaker box has a long cord that is sufficient to reach the campground eclectic post. Most campgrounds have a 50A, 30A and 15A receptacle. From the add on breaker box I ran the Hot Rod wiring to a switch mounted near the bathroom vanity. The switch has a red light to indicate when it is on. This way we can easily turn the Hot Rod on or off as needed.
I might add that we only turn the propane & electric on for the hot water tank as needed. Overnight we never leave the hot water tank running.