if you are doing all of the diffusing upside down, you might not be able to see in the mirror and do random sections may be- if that makes any sense. eventhough you saw frizz, I am sure you got great volume again a tradeoff!! I wish it was just easier get both definition and volume and no frizz.lol

If you want you can try starting on diffusing straight up for about 20% diffusing by section then do upside down diffusing, I have seen difference when I would do this way, volume on top without giving it to frizz

hope this helps
3a with some 2a-2c, Medium/Low Porosity
Co-wash:deva no-poo/Vo5 kiwi
Leave-in:Shea Moisture/GVP conditioning Balm/AOHSR

Since long hair- I finger twist in big chunks, which helps till 5th day hair
Gel:LA sports
Plop: Old T-shirt for 15 minutes ,diffuse