| Agree with Festa. I wouldn't steam or jet wash either.
I use Gunk on the tough stuff, Muc-off and the more softer muck and wash off with one of those plant sprayers. There's a reasonable amount of pressure but not a lot of flow, ie you don't get a lot of water everywhere and they're very controllable as to where the water goes.
the one I got holds 5 litres, you can even fill it with hot water. | 
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