1 Use an epoxy resin spray on cured pieces to cover indents or other imperfections. 2  You can also buff out imperfections with plastic polish and a buffing stick. 3  If air bubbles form in the mold, blow gently on them to pop them. 4  Wear gloves and work in a well-ventilated room.f it does show an indentation, leave to cure for an additional 1 to 2 days. Turn the mold upside down and lightly tap the back until the the resin piece emerges. Spread the resin pieces out on a sheet of wax paper and leave them to finish curing for an additional 12 to 24 hours before buffing or mounting.