These two techniques have helped to reduce volume for me:

Raking and smoothing in products, no scrunching! I also need to be careful when scrunching out the crunch, cause that when my volume starts to kick in. I don't scrunch upwards, but I put my hair in my hands as if I will make a ponytail and gently scrunch sideways.

Airdrying, I wish I had the time to airdry more often, it makes a big difference for me. Diffusing means more volume (and frizz)

Products that reduce volume:
These are my 2 favourite routines:
KCKT or KBB hair nectar as leave-in, KCCC as styler. I can go without a gel over it, although sometimes I use a bit of HEBE on top.
KBB hair milk, rinsed out, kbb hair nectar as leave-in. HEBE on top.
I don't know if you ever used coconut milk. My hair hangs better when I've done a dt with coconut milk.

I have 3B/3C curls, I'm really not sure about texture and porosity. I'm thinking medium texture (always thought I was coarse, but my hair likes protein) and high porosity.
medium/coarse and porous

wash: KC Come Clean, Flower Peddler Northern Lights soap bar
conditioner: YTT, YTC, KCKT, Shescentit GT&H, Shescentit Avocado, DB Pumpkin Seed, Garnier Ultra Doux, Mop Top daily conditioner
styler: KCCC, HEBE, homemade fsg, DM MCCG, AOMM
dt: banana and avocado mask, nexxus emergencee, Shescentit TT&GH, ayurvedic powders, SS RPT
butters: Jane Carter N&S, Afroveda Curly Custard, Afroveda Cocolatte, Shescentit Gillian, Shescentit Seyani