Due to the large size and complex structure of modern networks, firewall policies can contain several thousand rules. The size and complexity of these policies require automated tools providing a user-friendly environment to specify, configure and safely deploy a target policy. When activated in online mode, a firewall policy deployment is a very difficult and error-prone task. Indeed, it may result in self-Denial of Service (self-DoS) and/or temporary security breaches. In this paper, we provide correct, efficient and safe algorithms for two important classes of policy editing. Our experimental results show that these algorithms are fast and can be used safely even for deploying large policies.