Good question! I was wondering that.
I currently have to drive through a building site to get to the road, and need to do some cleaning underneath.
I will be honest, not easily!
It wasn't on a lift...I am pretty tall so have a relatively long reach, but it was mainly myself on my side half under the car, lying in a freezing cold puddle of chemicals and dirt, with a wash mitt selection and some Wheel Woolies for the hard to reach places, I will be honest I cut both arms and shoulders to bits on the sharp ally..