The complex geometries enabled by additive manufacturing (AM) create significant challenges for post-processing operations. Optimizing specific methods such as depowdering and particle-based surface finishing (e.g., tribofinition, sandblasting, vibropeening) is particularly difficult. Numerical simulations offer considerable advantages for accelerating the development and addressing quality issues associated with these techniques. Traditionally developed through empirical testing, post-processing processes require precise parameter definition (e.g., movement, vibration, part kinematics, media characteristics, particle velocity, impact angle, etc.) based on part geometry and material properties. This is especially critical for tribofinition, where media interaction with complex surfaces determines final quality [1, 2]. Simulation-assisted parameter optimization drastically reduces experimental testing while providing comprehensive information at any point on the part. Numerical models enable accurate estimation of treatment uniformity via coverage rate, contact distribution and pressure forces across all particle-based post-processing methods. The high computational cost of discrete element simulation has traditionally limited its use for industrial-scale granular systems. To overcome this computational barrier, this work introduces a novel granular solver leveraging GPU parallelization. This approach drastically reduces computation times and costs while maintaining simulation accuracy, making it viable for analyzing particle-based post-treatments at production scales. Case studies will primarily focus on tribofinition applications in various configurations (vibrating bowls [3], drag finishing, hexagonal barrel tumbling, complex media distributions), while also highlighting how the same simulation technology extends to sandblasting parameters optimization and vibropeening process development. Additionally, we'll demonstrate applications to depowdering challenges in complex geometries where it can be difficult to remove powder grains from internal channels. These advances significantly enhance industrial maturity of post-processing techniques for additively manufactured parts, optimizing both efficiency and profitability across the full range of particle-based finishing operations.