What I do is to cut away anything that is big enough to be cut with side cutters, then I scrape a bit with a knife, then I tidy up the casting with a fibre glass pencil also known as a scratch brush. I bought mine at Shesto (www.shesto.com - search for SCRATCH BRUSHES on thir site). I have the 2mm clutch type that takes refills. This is the best tool for cleaning of all metal objects.