This depends on the type of paint. We do not recommend pouring over an oil-based stain/paint. If you have already used an oil-based stain or paint, you can apply a water-based clear coat (must be water-based). Once the water-based clear coat has fully cured, you can apply the epoxy. If the clear coat leaves a shine/gloss you may want to scuff the surface to ensure the epoxy properly sticks. We recommend using 320 grit sandpaper. If you do sand, be sure to thoroughly clean the surface prior to applying the epoxy. We recommend using Isopropyl Alcohol 99% (be sure it is 99%) to clean. When in doubt, email us with specific questions.