Post process blur / render targets etc.

I’m looking to make a blur/decay previous frame blur effect but im stuck on what i think is the last step

im attempting to get something like this Unreal Engine Multipass Post Processing #2 - YouTube

ive gotten the materials and blueprints set up as follows

Player Begin Play

Player Event Tick


im not sure if its useful to know or not but if i change the ‘current’ node in the material to a panning texture its doing what i expect, but i cant get it to do the same thing with an rt source