Thanks! Yeah thats roughly how I have been doing it, but its time consuming and if there are any changes to the sequence or precomp, the triggered “effect” keyframes need to be repositioned.
A thought: Is it possible to parent a keyframe’s position in time ? In the example I gave above, if I had a keyframe at the start of each image that was parented to a keyframe in the “effect” layer (using it for its timecode)? that might take out a step at least. (…if that makes any sense)