A fast way to apply stroke offset animation to multiple lines

Hi there,

Hoping someone can help me with this. I deal with a lot of these types of flowcharts and am often looping the dash on the arrow lines for illustrative effect. I can do it manually obviously but its tedious to do for many layers. What would people suggest would be the fastest approach for this. I'm importing these lines from illustrator so can have the dash and gap set to the same for each layer though I can only seem to set the first dash and gap for it to transfer via overlord into AE which means the offset has to be manually added for each layer in AE as far as I can see.

I've tried copying and pasting to layers, that's fine for the loop out expression but not the keyframes for the offset. Ideally I'd like a trim paths but cannot copy and paste the trim paths from one shape layer to the next. I could live with a fade in instead of this however so that's not essential. I've tried using an animation preset but didn't manage to get that to work. 

If anyone had a fast way of applying a looping offset for many dashed lines I'd be greateful.

Thanks