One or two wheel weights would probably work just as well as bar lead.If I ever have need to give a brass part an even and bright patina, I'll use some old cleaning solution and a bar of lead after polishing the part(s).
Just put it in the solution with the parts you want darkened.
I learned about this by forgetting to remove the lead balls from an anniversary clock pendulum I was removing the lacquer on and attempting to brighten up a bit in the Purple Power. I left it in while I was out of town for a couple of days and it was a nice shiny caramel color when I pulled it out. Doing this ruins the solution unless you want to keep it for only this purpose.