I use a simple propane torch. One of those you can get at "X" hardware for ~ $10 or so. If you want to melt a bunch really fast, use a weed burner. You can buy those for about $15 or so at Harbour Freight. Just make sure you have something under the lead where you are burning to catch the drips. A piece of angle iron works well. You just want to make sure your receptacle will fit into your pot in one dimension or another. Don't worry about heating the lead up so far you will get vapors. The lead melts and drips away long before you reach that temperature.
When I'm in a hurry, I also use the propane torch to help heat the pot to get the lead melted and up to temp more quickly. FWIW...Pilgrim