1. the most important tip first: Wash your mountain bike immediately after the tour. In other words, when the dirt is still damp and not caked on. This will save you time and detergent.
2. use the no high pressure cleaner. This is generally not good for bearings, headset and seals on the bike.
3 It is best to carry out cleaning work at an official washing station so that as little detergent as possible is released directly into the environment.
4 If the dirt is a little older, soak your mountain bike first. To do this, mix hot water with a little all-purpose cleaner or washing-up liquid in a 10-litre cleaning bucket. Important: Only use a cleaner that is completely biodegradable. For example: Frosch all-purpose cleaner or Kinessin all-purpose cleaner. They are cheap and can be bought in any supermarket.
Bike doctor Dan Milner shows how to wash and clean your bike. Video in English.