yep, I've used a coleman camp stove, pull the grid up and set the pot right on the burner, another thing is with my set up I never mentioned is that I have a sheet metal cylinder around the pot, this gets the heat right to the metal and it melts a lot faster,
the way I understand it is that wheel weight are made with different alloys depending on who makes them, so you got to make your own judgement. Lyman gives a recipe of 9 lbs of wheel weight and 1lb of 50/50 solder for no 2 alloy.