What are the easiest permissible ways for ghusl (ritual bath) according to Sharia, and is sequential order (tartib) required in ghusl? What is the ruling on turning the tap off and on several times in case of doubt about wudu (ablution) or ghusl, and what is the solution for the obsessive whisperings (waswas) of repeatedly re-performing ghusl?

The description of ghusl (definition) (ritual bath) from major ritual impurity (janabah (definition)) is detailed in Al-Mughni. One should adhere to it and disregard obsessive thoughts (waswas) about having missed a part of the ablution (wudu). There is no need to repeat the ghusl or keep turning the water on and off repeatedly. All of that is from waswas, the cure for which is to ignore them and seek Allah's help. It suffices to turn on the faucet once for the ghusl, and it is not necessary to wash the body with water and soap before the ghusl. The cure for waswas is to seek refuge in Allah from Satan, make supplication, and ignore them.