Not sure if it would work as I have never tried it but some of the Harley lads used to use shower caps over their brake discs if they were having a major clean, they would drop the wheel out and pop one or two on (with twin discs) and pressure wash away. I never saw the point as if your cleaning that well buy some brake cleaner and clean the disc up afterwards anyway. I prefer a cardboard shield and some degreaser and a paintbrush then some warm water in a 'rose sprayer' to wash off and finish with an airline, then I give the rebound Spring a good soak in motorbike chain lube before rebinding with a leather shroud and cable ties.
