While you're at the dollar store you may want to also pick up a stainless steel slotted spoon for removing the clips, steel/zinc wheel weights, and flux from the top of your melt. I use sawdust for my initial flux, a few handfuls adding at the start of the melt. Then once the lead is melted, I add some candle wax and light it up. The clips come out perfectly clean, and the "dross" is just a grey light powder.
I don't sort my wheel weights, but I usually remove the tire stems and other rubber items out of respect for the neighbors. I never let my melt get quite hot enough to melt pure lead. I keep a few lead stick-ons in there, and the most they'll get is just a bit ragged at the edges toward the end when I've gotten almost all the non-meltables out. This ensures that my melt never gets near hot enough to melt the zinc ones.
I too use muffin tins for ingot molds. They take awhile to cool, so at least 2 of them work best. I like the small muffin ones, because they allow you to top up your pot more often without waiting for it to heat back up.