So I'm creating a light-writing video like this one I made (but more elaborate):
happybirthday.mp4 on Vimeo

I made this by duplicating the video layer
-using curves to isolate the flashlight
-then Echo set to Maximum with about 70 echos,
I render that out, then bring it back in and echo it some more until it covers the length of the video, then screen it on to the original footage.

My question is this:

Does anyone know of a better/faster way of doing this? It's super slow considering I have over 1/2 an hour of footage to render.

I can understand why the echo effect is resource hungry, but I thought that if I'm using it on a black & white image with small dot of moving pixels would speed it up some.

Or perhaps it's the H264 footage aftereffects if reading from my canon DSLR?

Any workflow suggestions here?

Hi Stephen. You might find it would work to save each letter/object as a still image, mask each one down and fade each up as its echo completes. That way you only have to have the echo effect used once and the letters will remain as still images. Should work?