Either your lead is not hot enough or the mold is contaminated with oil. Most likely it's the lead temperature.

Don't worry about not having the flux flame. It's not at all necessary and its only benefit is to burn off the smoke/smell. I don't flux my lead at all - just get it real hot, stir and skim. I stir the lead with a ten inch piece of heavy wire mounted on a wood handle cut from a piece of broomstick. Stir and skim, stir and skim, etc. A point is reached where no crud comes to the top when stirred, and the lead is perfectly clean.

What type of set up are you using? Burner/pot/ladle? Electric pot?