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a pressure washer
I mean they're great things to have, but I personally wouldn't use one on a bike. There's too much risk of the blast getting into bearings and other nooks and crannies.
Screwfix degreaser, a stiff round sash type paint brush plus one of those brutal plastic bike ones is a better idea imo.
Also just in case you didn't know, if you buy a Kärcher pressure washer you're meant to refer to it as a Kärcher rather than a pressure washer, to make sure people know you bought a Kärcher ;)
Mine was absolutely caked the last time I removed it, but I like having the protection to stop things getting stuck in there.