I used a Flush King or Hydro Flush with separate snap on valve when I had our hybrid. Worked great for years. Uses a lot of water to fill, drain, fill, drain until all gunk is out but kept tank clean.
2014 Winnebago 26FWRKS 5th Wheel
2007.5 Dodge 2500 6.7L Diesel
2004 Dodge Durango Hemi 3.55 (Used to tow TT)