I also start cleaning painted machines with Dawn dish soap (damp cloth)and use Meguiar's #10 mirror glaze to finish the cleaning. I just tested a strong cleaner for a plastic case that was very dirty and had black shoe type marks. It is Krud Kutter from HD, my wife uses it for cleaning tile grout. The results was remarkable and the case now looks nearly new. It worked so well I plan on testing this product on a machine in the future. I will post results once it has been tested.