If anyone is having trouble chain weaving Tifa's LB, a Japanese youtuber called Tarowan has actually made a very detailed guide about it a while ago. He goes through the different chain groups in slow motion and tells you what visual cues to look for.

https://www.youtube.com/watch?v=9DK6Xz9z-0g

I'll give a quick translation of tips on how to chain on BS form since that's what most people are interested in.

Lucent Glaive/AMoE/BS-Tap Tifa right after you tap the chainers. Tarowan says that the timing for LG/AMoE can be very tricky.

CWA-Tap Tifa after you see the chains start to build. I usually start the LB after I see around 5-6 chains and it's been working perfectly so far.

Rain&Fina-Tap Tifa right after Rain&Fina jumps and reaches the highest point in the air. Tarowan also mentions that ability tag chains won't work with Tifa.

SR-Tap Tifa right after you see the chainers start their 3rd cast.

Flood-Tap Tifa right after you see the 2nd set of Tidal waves.

I hope this helps, and feel free to let me know if these tips actually work for you guys.