I have found that gravity, ~2m of 18mm OD clear plastic tube and a funnel works great. Preheat both the old and new fluid(Istore the new in my heating room between the boiler and hot water heater), the car should be level so I use 4 jackstands. The funnel is hung from the rafters at a convienient height, the clear tube allows observation of the progress(or not) of the fluid. it is generally a clean, hassle free project. the stain on the floor is solely from inattention.
