My aluminum molds, including the many MP versions I have, get solvent cleaned to remove any cutting oils and go right to work, but we're talking about brass molds here, right (at least it's my impression that all of Miha's HP molds are brass)? I only have two brass molds in calibers I don't shoot often so they haven't been used yet, but, correct me if I'm wrong, I thought the patina on brass molds is helpful in preventing tinning.