Do you use MAC Fix Plus before or after makeup?

Could you please clarify for me - when exactly is the optimal time to apply MAC Fix Plus, before or after makeup application? I'm interested in understanding if it serves as a primer to prep the skin before makeup, or if it's intended to be used as a setting spray to lock in the makeup after it's been applied. I'm sure many makeup enthusiasts would benefit from this clarification, as the right timing can significantly impact the overall look and longevity of their makeup.