We started finishing our magnum board wall and ceiling panels this week. We are using a magnesium powder+ 200-300 grit sand + water mixture for our finishing material. We use this combination in replace of the typical drywall joint compound.. This is a non toxic, mold proof, water proof and breathable alternative to the accepted standard. The material is a bit more expensive but we feel that the benefits far outweigh the additional cost of the material.