Just one thing I'd like to point out. "Dish soap" or dish detergent is not the same as soap as in bar soap.
You want to use bar soap to clean your ML not a de-greasing detergent.
After hot water cleaning the bare steel bore will quickly rust over there is no stopping it. But it is so light that it comes off with a oiled or bore butter lubed patch. The first lubricating patch after cleaning a steel barrel will almost always have a rust tint on it.
Motor