I think someone posted here a few months ago about using stearic acid. I got some of e[vil]-bay and a little dab will do ya. I have used marvelux, pine resin, sawdust, and paraffin. Paraffin is cheap, but stearic acis really cleans up my melt.
Here's a reference.
http://www.answers.com/topic/stearic-acid
Just my 2 grains worth...