[Unreal 4.27] Ambient Occlusion look using Before Tonemapping

Hello!

I’m trying to apply a post process volume that gives an ambient occlusion look to my entire scene. I’m using a simple material for that and it works great if I’m setting it to be after tonemapping. Which sucks because I’m losing TAA, DLSS… So I switched to before tonemapping but the effect doesn’t work at all. Any idea on how to modify my material so that it looks as good ? I even tried to apply the material Epic uses for the Buffer Visualization:AO but all I get is a big white screen.