I clean them by soaking the wheel in a 50/50 solution of MOTO-Xtreme cleaner. Leave overnight then clean each spoke off with a non stick brillo pad. Seems to work for me but it is a right pain in the arse and my least favorite job. Like others have said the spokes are so cheap and really need replacing if you can afford it (which i generaly can't!).

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Why when you can