you can attempt to do this - it wont be the prettiest job as fluid moves quite quick in those lines and you still have to measure the level from under the car anyway.

Two garden sprayers connected together can be a good flushing solution, one tank collects the old fluid while the other is simultaneously pushing new fluid in.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)