I've used sawdust for years. Once my lead has melted I stir in a heaping tablespoon of sawdust and work it into the melt with tablespoon that I have small holes drilled into to allow the spoon to flow through the lead easily. Once charred and stirred in well I let the char stay on top to help prevent oxidation and don't remove it till I'm ready to add more led to the pot.
Most likely a "duh" question here, but you're using a bottom pour spout, correct?
