A candle will do in a pinch for a mold lube. The reason for the mold lube is that hot aluminum gets "sticky" and doesn't want to close or open easily.
Usually a one time smoking is all that is required.
You might wash the mold with acetone or lacquer thinner or strong alcohol before you smoke it.
Make sure that the lead, dead soft, that you are using is very clean. Multiple fluxings before you begin to cast. Dirty lead will eat the thin aluminum at the sprue away and give you a very ugly outcome. (Don't ask how I know and don't ask why it took a couple of ruined molds for me to figure that out