Polyester resin can be used for repairs on SMC (Sheet Molding Compound) and fiberglass panels and parts, especially when used with fiberglass mat, cloth, or tape.
The most important step is removing any residual mold release agent from the SMC surface. This can be done by sanding with a 36 grit disc or a structured tooth bit, followed by wiping the area with acetone.
However, for structural repairs on SMC, using a product specifically designed for SMC is recommended.