No problem with sticking in any of the a fore mentioned materials. My Grand Father used to make lead pyramid sinkers, in a mold he made from a steel container, and he just used the store bought sinkers, of various weights, and put a frame above the container, and poured lime in it, and stuck the sinkers which had a little light oil on them, as a release agent for the lime, on a rod on the frame, and let the lime harden around the sinkers, and then he had a mould for sinkers. He would take the steel rod, and make little twisted copper eyelets, and run the rod through them, and put the rod in notches in the frame, and then pour the melted lead into the mould. We used to do it as kids. For the slag, when you pour the lead, put a couple of pieces of bees wax, or parafin, in it before it cools, and the slag will clump together, and you can skim it off.
Yeah, make sure the cans are steel, and not aluminum, and don't use too high a heat.
Wayne.