Extracing data buffers

but haven't found a way to put all the buffers into an text file,

There are several options to do that. See my answers to similar questions.

https://ask.wireshark.org/questions/38998/automating-extraction-of-udp-payload-from-pcap-file
https://ask.wireshark.org/questions/35353/exporting-payload-data-in-binary-file
https://ask.wireshark.org/questions/47183/bulk-extraction-of-udp-payload-data
https://ask.wireshark.org/questions/29693/export-selected-packet-bytes-how-to-cut-off-the-payload-in-a-pcap-file

that I can annotate later.

You can annotate the frame in Wireshark if it's a pcap-ng.

Right click a frame and select Packet Comment. Comments will be stored in the pcap-ng if you save the file.

Regards
Kurt