How do you use makeup fixer?

Excuse me, could you please elaborate on how you typically use makeup fixer in your beauty routine? I'm curious to know if you apply it before or after your foundation, and if there's a specific technique you follow to ensure it sets your makeup properly. Additionally, I'd love to hear about any benefits you've noticed from using makeup fixer, such as longer-lasting makeup or a more matte finish. Thank you for sharing your insights!