Well you are going to melt it usually in a ladle ( its pretty hard to get out of a lead pot) and it has to be done in a single pour. That not only tells you how much to melt, but how big your nosecap can be. I use modern pewter that is lead free. The junk stores are full of it. It will say lead free, and will often be engraved as some sort of recognition, or trophy. Flagons, trays, candy dishes, are all good stuff. Stay away from things with multiple parts that are soldered together, the solder creates a problem.
Be sure to skim the dross off before you pour, and pour as soon as the pewter liquifies and looks like chrome. If you heat it too long it will develop air bubbles. Good luck.
The rod down the barrel is a good idea, especially on heavy barrels, a heated rod can make the difference between a nosecap, and one heck of a mess.
Hungry Horse