Found some very weathered (grungy and dirty) Peco rail joiners which I wanted to re-use - tried several ways to clean them, but not very successfully. Eventually came up with an idea that I bet some members have also used. Put the joiners in a glass jug, gave them a good squirt with Cillit Bang, swished them round, left them to soak for a few minutes, then gave them a good rinse -- came up like brand new!