How to have a global post process?

I need to add post process after the whole render, that includes the render of UI widgets, the current unreal way is pretty much inefficient (if not useless) for what im doing. Any idea? I already got the look working, but it requires 2 retainers in the widgets and duplicated code, for the whole post process. 3D widgets dont cut it since the “$·%·$&”$%· tonemapper messes with the brightness of the images in the 3D widget.