Which policy set should be used to ensure that a policy is applied just before...

The policy set that should be used to ensure that a policy is applied just before the default security rules is the shared post-rulebase. The shared post-rulebase is a set of Security policy rules that are defined on Panorama and apply to all firewalls or device groups. The shared post-rulebase is evaluated after the local firewall policy and the child device-group post-rulebase, but before the default security rules. The shared post-rulebase can be used to enforce common security policies across multiple firewalls or device groups, such as blocking high-risk applications or traffic1. References: Security Policy Rule Hierarchy, Security Policy Rulebase, Certifications - Palo Alto Networks, Palo Alto Networks Certified Network Security Administrator (PAN-OS 10.0) or [Palo Alto Networks Certified Network Security Administrator (PAN-OS 10.0)].