How to use the Charlotte Tilbury Setting Spray Properly

hello, I currently have the CT spray but unfortunately I’m not very sure how to use it properly. People are saying it helps make the makeup look dewy at the end and are usually using it by the end of their routine, but I find that I can only use it after all my creams and before my powder. If i try to use it after my powders, it tends to become patchy or cakey. Is there a right way to use this? My base products I usually use are the Laura Mercier Loose Powder in Rose and Issy Foundation (from the Philippines). I have tried it with different products and it does the same thing, even with the Urban Decay foundation (their old version). I find this odd because I can use my older setting spray with my powder on just fine.