Film mix from a unique soundtrack file

Hello,

I have to do the mixing of a 90-minute documentary. The team delivered me only 3 files of 90 minutes each, from their FinalCut Pro X session:
- Video in mp4
- The "musics" track in wav
- The "direct sounds" track in wav (interviews, live sound, cutaways etc, all in a row on the same track)

So I split the direct sounds track into several pieces (practically one piece per shot or per sequence) in a multitrack session.
But if I apply an effect to one piece, it applies it to the entire 90 minute wav file.
How do I do the mix shot by shot, with different effects on each "piece" of the clip?

Thank you for your help