Electroadhesion provides a reversible adhesion based on electrostatic attractive forces between a substrate and an electroadhesive pad, enabling the handling of various objects. Despite its structural simplicity and broad applicability, conventional electroadhesion systems often suffer from relatively low adhesive forces and strong performance variability depending on substrate properties, which limits their practical use. To address these limitations, this study proposes a new electroadhesion operating protocol that integrates voltage application, interfacial sliding, and subsequent voltage removal. Experimental results demonstrate that the proposed protocol increases pull-off force by up to 367% compared to the conventional operating method for metallic and ceramic substrates, with particularly pronounced enhancement on rough surfaces as well as in the low-voltage regime. Furthermore, the effects of voltage application conditions, surface roughness, and sliding conditions on adhesion performance were systematically investigated. The results reveal that adhesion enhancement is strongly governed by material and surface properties, with the most significant gains observed for rough metallic and ceramic substrates, while requiring only a single sliding cycle to achieve performance gains. Based on these findings, a robotic manipulation demonstration was conducted in which a robotic manipulator successfully transferred a 1125 g glass plate for more than 20 consecutive cycles. This work presents an operating protocol for enhancing electroadhesion performance without modifying pad geometry or materials, with demonstrated effectiveness for metallic and ceramic substrates, providing a practical pathway toward improving the load-carrying capability and robustness of electroadhesion-based handling systems.