I haven't found any resources online, which is a little odd. After all it's readily available in filament form and not too expensive. Hopefully this will eliminate the need for a high-temperature burnout, at least for low-melting metals like pewter and lead. Now, being water soluble it will have to be protected during the investment casting. Something like nitrocellulose lacquer should be perfect. I have also seen PCB coatings that will burn off cleanly during soldering. The high solubility should also allow for simple vapor smoothing, which is the biggest downside to using PLA. Just look at this little figurine cast in lead: The level of detail is incredible, so all the layers stand out like sore thumbs.