I was picking up some lead (Linotype WW mix) from a guy that was getting out of casting. He had plenty of boolits and was old enough he decided to move on. While I was picking up the lead he offered me all kinds of stuff. I ended up with two Lee 6 cavity moulds. They looked pretty good the way he was holding them so I thought, "what the heck". When I got them home I swung the sprue plate over on one and was shocked to see how dirty the top of the mould was. The build up was so thick no amount of WD40 or other solvents would remove it. I ended up using a flat plate and some 400 grit sand paper to get it off. I polished it with 800 grit and hoped I didn't mess it up. The mould looks great now and is very smooth but the sprue plate was just as bad. I gave it the same sand/polish and it looks great and swings very smooth. I am pretty new to casting so I have to ask if this was the way to handle it? The other mould is dirty but not as bad. The buildup looks like baked on lubricant of some kind. There is a little in two of the cavities that won't budge with a toothpick but it doesn't look very thick so I will find out with a little casting if it will effect the boolets. So my question is do I give the other mould the same treatment?