Flushing water lines after use is usually not necessary.
The sulfur smell is a common issue with water heaters. It's from anaerobic bacteria that exists in some water sources. Draining the water heater and/or sterilizing the fresh water system with bleach should take care of it.
Sherm & Terry w/rescue Eydie (min Schnauzer) & Charley (std Poodle)
2015 Jay Flight 27RLS (Nights Camped: 102 '15, 90 '16, 80 '17, 161 '18)
2006 Ford F350 6.0 PSD, 4WD, CC, LB, SRW, Camper pkg, Equal-i-zer, GY Endurance (E)