Camera water droplets post process effect?

Wondering if anyone knows how it would be possible to create a material to display water droplets on the screen. Like this:

There is a thread on the UE4 forums, which make it look kind o easy: Water on camera lense effect - Rendering - Unreal Engine Forums

But there are some nodes the are using that i don’t see in UDK (like PostProcessInput).

Any ideas on how I can get this working in UDK?