When I melt wheel weights, I usually use a very large Iron pot and a propane burner. after the wheel weights have melted to a liquid state I flux them.
To Flux I use Beeswax. I just toss in small piece and stir with very large spoon. This will bring all of the dross and pieces of metal to the surface to be removed.
If you remove the metal and the dross from the surface without fluxing you will remove some of the tin and antimony. and if you continue scooping the shiny stuff off the top you are removing tin, a needed ingredient for hardness, and it makes pouring a lot smoother.
I have several tons of the stuff all mixed with tin (from 95/5 solder). I was using it when I was making bullets for myself and my shooting buddies.
I use the same lead/tin mixture for making lead jig heads and catfish weights.
When melting wheel weights or any lead mixture, be sure that there is no moisture present, if there is and you put some in the mixture you will remember doing so for a long time. I know, I put a wet ladle in melted bullet metal back in the early '60's. I was lucky to only get a few scars! I didn't once think that that little bit moisture would hurt anything.