My problem is only with Smoothon 300 resin with their RTV rubber and spray can mold release. The parts come out with an indestructible glossy sheen. I'v tried thinners, strippers, alcohol, gasoline, every strong chemical I could find around the house. Even swimming pool acid. Nothing works.
Thought there might be a product I didnt know about.
I've found that once resin parts are flat primed, they will be flat when finished painted with flats. I do use alternating enamels and acylic method: base colors enamel and weathering and rusting, acrylic.