We use a urethane resin instead of polyester as it is stronger, nearly bubble-free and has no odor during the casting process.
There are a number of methods to remove the last of the mold release residue that remains on the castings so that your paint will adhere to the castings and here are some methods that are being used.
Method #1...3 to 4 gallons of water...add dawn dish detergent....1/4 cup of Pine Sol ...place the castings in the mixture and leave overnight.
Method #2.... 3 to 4 gallons of water..add white vinegar and again let the castings soak for a number of hours.
Method #3.....Fill sink with warm water and add dish detergent...scrub with old tooth brush...empty sink..wash off castings.
Fill sink again...add dish detergent...add same castings again... and walk away for several hours..don't try to do too many castings at a time.
We recommend that you spray the castings with Rustoleum American Accent 2X Ultra Cover...Flat Black or Dark Brown over the black if doing wood finishes. Then, finish the castings using either an acrylic or oil-based paint, or a combination of both. Then, as the final stage, spray the casting with a matte sealer.