The lube will be a good flux. When the melt starts to smoke throw a lit match in it to ignite it; otherwise you might get a big surprise when it ignites on it's own. Sounds like you need to do more reading on casting. Here is 1 good place to start.
. Gunloads.com is another. There is also a sub forum above this one for casting. Good Luck and enjoy the addiction. You will have a lot more questions as you continue the hobby.